bpo-31370: Remove support for threads-less builds (#3385)

* Remove Setup.config
* Always define WITH_THREAD for compatibility.

81 files changed, 2372 insertions, 3387 deletions

diff --git a/Lib/_dummy_thread.py b/Lib/_dummy_thread.py
deleted file mode 100644
index a2cae54..0000000
--- a/Lib/_dummy_thread.py
+++ /dev/null
@@ -1,163 +0,0 @@
-"""Drop-in replacement for the thread module.
-
-Meant to be used as a brain-dead substitute so that threaded code does
-not need to be rewritten for when the thread module is not present.
-
-Suggested usage is::
-
-    try:
-        import _thread
-    except ImportError:
-        import _dummy_thread as _thread
-
-"""
-# Exports only things specified by thread documentation;
-# skipping obsolete synonyms allocate(), start_new(), exit_thread().
-__all__ = ['error', 'start_new_thread', 'exit', 'get_ident', 'allocate_lock',
-           'interrupt_main', 'LockType']
-
-# A dummy value
-TIMEOUT_MAX = 2**31
-
-# NOTE: this module can be imported early in the extension building process,
-# and so top level imports of other modules should be avoided.  Instead, all
-# imports are done when needed on a function-by-function basis.  Since threads
-# are disabled, the import lock should not be an issue anyway (??).
-
-error = RuntimeError
-
-def start_new_thread(function, args, kwargs={}):
-    """Dummy implementation of _thread.start_new_thread().
-
-    Compatibility is maintained by making sure that ``args`` is a
-    tuple and ``kwargs`` is a dictionary.  If an exception is raised
-    and it is SystemExit (which can be done by _thread.exit()) it is
-    caught and nothing is done; all other exceptions are printed out
-    by using traceback.print_exc().
-
-    If the executed function calls interrupt_main the KeyboardInterrupt will be
-    raised when the function returns.
-
-    """
-    if type(args) != type(tuple()):
-        raise TypeError("2nd arg must be a tuple")
-    if type(kwargs) != type(dict()):
-        raise TypeError("3rd arg must be a dict")
-    global _main
-    _main = False
-    try:
-        function(*args, **kwargs)
-    except SystemExit:
-        pass
-    except:
-        import traceback
-        traceback.print_exc()
-    _main = True
-    global _interrupt
-    if _interrupt:
-        _interrupt = False
-        raise KeyboardInterrupt
-
-def exit():
-    """Dummy implementation of _thread.exit()."""
-    raise SystemExit
-
-def get_ident():
-    """Dummy implementation of _thread.get_ident().
-
-    Since this module should only be used when _threadmodule is not
-    available, it is safe to assume that the current process is the
-    only thread.  Thus a constant can be safely returned.
-    """
-    return 1
-
-def allocate_lock():
-    """Dummy implementation of _thread.allocate_lock()."""
-    return LockType()
-
-def stack_size(size=None):
-    """Dummy implementation of _thread.stack_size()."""
-    if size is not None:
-        raise error("setting thread stack size not supported")
-    return 0
-
-def _set_sentinel():
-    """Dummy implementation of _thread._set_sentinel()."""
-    return LockType()
-
-class LockType(object):
-    """Class implementing dummy implementation of _thread.LockType.
-
-    Compatibility is maintained by maintaining self.locked_status
-    which is a boolean that stores the state of the lock.  Pickling of
-    the lock, though, should not be done since if the _thread module is
-    then used with an unpickled ``lock()`` from here problems could
-    occur from this class not having atomic methods.
-
-    """
-
-    def __init__(self):
-        self.locked_status = False
-
-    def acquire(self, waitflag=None, timeout=-1):
-        """Dummy implementation of acquire().
-
-        For blocking calls, self.locked_status is automatically set to
-        True and returned appropriately based on value of
-        ``waitflag``.  If it is non-blocking, then the value is
-        actually checked and not set if it is already acquired.  This
-        is all done so that threading.Condition's assert statements
-        aren't triggered and throw a little fit.
-
-        """
-        if waitflag is None or waitflag:
-            self.locked_status = True
-            return True
-        else:
-            if not self.locked_status:
-                self.locked_status = True
-                return True
-            else:
-                if timeout > 0:
-                    import time
-                    time.sleep(timeout)
-                return False
-
-    __enter__ = acquire
-
-    def __exit__(self, typ, val, tb):
-        self.release()
-
-    def release(self):
-        """Release the dummy lock."""
-        # XXX Perhaps shouldn't actually bother to test?  Could lead
-        #     to problems for complex, threaded code.
-        if not self.locked_status:
-            raise error
-        self.locked_status = False
-        return True
-
-    def locked(self):
-        return self.locked_status
-
-    def __repr__(self):
-        return "<%s %s.%s object at %s>" % (
-            "locked" if self.locked_status else "unlocked",
-            self.__class__.__module__,
-            self.__class__.__qualname__,
-            hex(id(self))
-        )
-
-# Used to signal that interrupt_main was called in a "thread"
-_interrupt = False
-# True when not executing in a "thread"
-_main = True
-
-def interrupt_main():
-    """Set _interrupt flag to True to have start_new_thread raise
-    KeyboardInterrupt upon exiting."""
-    if _main:
-        raise KeyboardInterrupt
-    else:
-        global _interrupt
-        _interrupt = True
diff --git a/Lib/_pydecimal.py b/Lib/_pydecimal.py
index edabf72..a43c75f 100644
--- a/Lib/_pydecimal.py
+++ b/Lib/_pydecimal.py
@@ -436,75 +436,34 @@ _rounding_modes = (ROUND_DOWN, ROUND_HALF_UP, ROUND_HALF_EVEN, ROUND_CEILING,
 # work for older Pythons.  If threads are not part of the build, create a
 # mock threading object with threading.local() returning the module namespace.
 
-try:
-    import threading
-except ImportError:
-    # Python was compiled without threads; create a mock object instead
-    class MockThreading(object):
-        def local(self, sys=sys):
-            return sys.modules[__xname__]
-    threading = MockThreading()
-    del MockThreading
-
-try:
-    threading.local
-
-except AttributeError:
-
-    # To fix reloading, force it to create a new context
-    # Old contexts have different exceptions in their dicts, making problems.
-    if hasattr(threading.current_thread(), '__decimal_context__'):
-        del threading.current_thread().__decimal_context__
-
-    def setcontext(context):
-        """Set this thread's context to context."""
-        if context in (DefaultContext, BasicContext, ExtendedContext):
-            context = context.copy()
-            context.clear_flags()
-        threading.current_thread().__decimal_context__ = context
-
-    def getcontext():
-        """Returns this thread's context.
-
-        If this thread does not yet have a context, returns
-        a new context and sets this thread's context.
-        New contexts are copies of DefaultContext.
-        """
-        try:
-            return threading.current_thread().__decimal_context__
-        except AttributeError:
-            context = Context()
-            threading.current_thread().__decimal_context__ = context
-            return context
+import threading
 
-else:
+local = threading.local()
+if hasattr(local, '__decimal_context__'):
+    del local.__decimal_context__
 
-    local = threading.local()
-    if hasattr(local, '__decimal_context__'):
-        del local.__decimal_context__
+def getcontext(_local=local):
+    """Returns this thread's context.
 
-    def getcontext(_local=local):
-        """Returns this thread's context.
-
-        If this thread does not yet have a context, returns
-        a new context and sets this thread's context.
-        New contexts are copies of DefaultContext.
-        """
-        try:
-            return _local.__decimal_context__
-        except AttributeError:
-            context = Context()
-            _local.__decimal_context__ = context
-            return context
-
-    def setcontext(context, _local=local):
-        """Set this thread's context to context."""
-        if context in (DefaultContext, BasicContext, ExtendedContext):
-            context = context.copy()
-            context.clear_flags()
+    If this thread does not yet have a context, returns
+    a new context and sets this thread's context.
+    New contexts are copies of DefaultContext.
+    """
+    try:
+        return _local.__decimal_context__
+    except AttributeError:
+        context = Context()
         _local.__decimal_context__ = context
+        return context
+
+def setcontext(context, _local=local):
+    """Set this thread's context to context."""
+    if context in (DefaultContext, BasicContext, ExtendedContext):
+        context = context.copy()
+        context.clear_flags()
+    _local.__decimal_context__ = context
 
-    del threading, local        # Don't contaminate the namespace
+del threading, local        # Don't contaminate the namespace
 
 def localcontext(ctx=None):
     """Return a context manager for a copy of the supplied context
diff --git a/Lib/_pyio.py b/Lib/_pyio.py
index 4653847..1e105f2 100644
--- a/Lib/_pyio.py
+++ b/Lib/_pyio.py
@@ -9,10 +9,7 @@ import errno
 import stat
 import sys
 # Import _thread instead of threading to reduce startup cost
-try:
-    from _thread import allocate_lock as Lock
-except ImportError:
-    from _dummy_thread import allocate_lock as Lock
+from _thread import allocate_lock as Lock
 if sys.platform in {'win32', 'cygwin'}:
     from msvcrt import setmode as _setmode
 else:
diff --git a/Lib/_strptime.py b/Lib/_strptime.py
index fe94361..284175d 100644
--- a/Lib/_strptime.py
+++ b/Lib/_strptime.py
@@ -19,10 +19,7 @@ from re import escape as re_escape
 from datetime import (date as datetime_date,
                       timedelta as datetime_timedelta,
                       timezone as datetime_timezone)
-try:
-    from _thread import allocate_lock as _thread_allocate_lock
-except ImportError:
-    from _dummy_thread import allocate_lock as _thread_allocate_lock
+from _thread import allocate_lock as _thread_allocate_lock
 
 __all__ = []
 
diff --git a/Lib/bz2.py b/Lib/bz2.py
index 6f56328..3924aae 100644
--- a/Lib/bz2.py
+++ b/Lib/bz2.py
@@ -14,11 +14,7 @@ import io
 import os
 import warnings
 import _compression
-
-try:
-    from threading import RLock
-except ImportError:
-    from dummy_threading import RLock
+from threading import RLock
 
 from _bz2 import BZ2Compressor, BZ2Decompressor
 
diff --git a/Lib/ctypes/test/test_errno.py b/Lib/ctypes/test/test_errno.py
index 4690a0d..3685164 100644
--- a/Lib/ctypes/test/test_errno.py
+++ b/Lib/ctypes/test/test_errno.py
@@ -1,10 +1,8 @@
 import unittest, os, errno
+import threading
+
 from ctypes import *
 from ctypes.util import find_library
-try:
-    import threading
-except ImportError:
-    threading = None
 
 class Test(unittest.TestCase):
     def test_open(self):
@@ -25,25 +23,24 @@ class Test(unittest.TestCase):
         self.assertEqual(set_errno(32), errno.ENOENT)
         self.assertEqual(get_errno(), 32)
 
-        if threading:
-            def _worker():
-                set_errno(0)
+        def _worker():
+            set_errno(0)
 
-                libc = CDLL(libc_name, use_errno=False)
-                if os.name == "nt":
-                    libc_open = libc._open
-                else:
-                    libc_open = libc.open
-                libc_open.argtypes = c_char_p, c_int
-                self.assertEqual(libc_open(b"", 0), -1)
-                self.assertEqual(get_errno(), 0)
+            libc = CDLL(libc_name, use_errno=False)
+            if os.name == "nt":
+                libc_open = libc._open
+            else:
+                libc_open = libc.open
+            libc_open.argtypes = c_char_p, c_int
+            self.assertEqual(libc_open(b"", 0), -1)
+            self.assertEqual(get_errno(), 0)
 
-            t = threading.Thread(target=_worker)
-            t.start()
-            t.join()
+        t = threading.Thread(target=_worker)
+        t.start()
+        t.join()
 
-            self.assertEqual(get_errno(), 32)
-            set_errno(0)
+        self.assertEqual(get_errno(), 32)
+        set_errno(0)
 
     @unittest.skipUnless(os.name == "nt", 'Test specific to Windows')
     def test_GetLastError(self):
diff --git a/Lib/dummy_threading.py b/Lib/dummy_threading.py
deleted file mode 100644
index 1bb7eee..0000000
--- a/Lib/dummy_threading.py
+++ /dev/null
@@ -1,78 +0,0 @@
-"""Faux ``threading`` version using ``dummy_thread`` instead of ``thread``.
-
-The module ``_dummy_threading`` is added to ``sys.modules`` in order
-to not have ``threading`` considered imported.  Had ``threading`` been
-directly imported it would have made all subsequent imports succeed
-regardless of whether ``_thread`` was available which is not desired.
-
-"""
-from sys import modules as sys_modules
-
-import _dummy_thread
-
-# Declaring now so as to not have to nest ``try``s to get proper clean-up.
-holding_thread = False
-holding_threading = False
-holding__threading_local = False
-
-try:
-    # Could have checked if ``_thread`` was not in sys.modules and gone
-    # a different route, but decided to mirror technique used with
-    # ``threading`` below.
-    if '_thread' in sys_modules:
-        held_thread = sys_modules['_thread']
-        holding_thread = True
-    # Must have some module named ``_thread`` that implements its API
-    # in order to initially import ``threading``.
-    sys_modules['_thread'] = sys_modules['_dummy_thread']
-
-    if 'threading' in sys_modules:
-        # If ``threading`` is already imported, might as well prevent
-        # trying to import it more than needed by saving it if it is
-        # already imported before deleting it.
-        held_threading = sys_modules['threading']
-        holding_threading = True
-        del sys_modules['threading']
-
-    if '_threading_local' in sys_modules:
-        # If ``_threading_local`` is already imported, might as well prevent
-        # trying to import it more than needed by saving it if it is
-        # already imported before deleting it.
-        held__threading_local = sys_modules['_threading_local']
-        holding__threading_local = True
-        del sys_modules['_threading_local']
-
-    import threading
-    # Need a copy of the code kept somewhere...
-    sys_modules['_dummy_threading'] = sys_modules['threading']
-    del sys_modules['threading']
-    sys_modules['_dummy__threading_local'] = sys_modules['_threading_local']
-    del sys_modules['_threading_local']
-    from _dummy_threading import *
-    from _dummy_threading import __all__
-
-finally:
-    # Put back ``threading`` if we overwrote earlier
-
-    if holding_threading:
-        sys_modules['threading'] = held_threading
-        del held_threading
-    del holding_threading
-
-    # Put back ``_threading_local`` if we overwrote earlier
-
-    if holding__threading_local:
-        sys_modules['_threading_local'] = held__threading_local
-        del held__threading_local
-    del holding__threading_local
-
-    # Put back ``thread`` if we overwrote, else del the entry we made
-    if holding_thread:
-        sys_modules['_thread'] = held_thread
-        del held_thread
-    else:
-        del sys_modules['_thread']
-    del holding_thread
-
-    del _dummy_thread
-    del sys_modules
diff --git a/Lib/functools.py b/Lib/functools.py
index 23ad160..25075de 100644
--- a/Lib/functools.py
+++ b/Lib/functools.py
@@ -22,13 +22,7 @@ from collections import namedtuple
 from types import MappingProxyType
 from weakref import WeakKeyDictionary
 from reprlib import recursive_repr
-try:
-    from _thread import RLock
-except ImportError:
-    class RLock:
-        'Dummy reentrant lock for builds without threads'
-        def __enter__(self): pass
-        def __exit__(self, exctype, excinst, exctb): pass
+from _thread import RLock
 
 
 ################################################################################
diff --git a/Lib/http/cookiejar.py b/Lib/http/cookiejar.py
index adf956d..e0f1032 100644
--- a/Lib/http/cookiejar.py
+++ b/Lib/http/cookiejar.py
@@ -33,10 +33,7 @@ import datetime
 import re
 import time
 import urllib.parse, urllib.request
-try:
-    import threading as _threading
-except ImportError:
-    import dummy_threading as _threading
+import threading as _threading
 import http.client  # only for the default HTTP port
 from calendar import timegm
 
diff --git a/Lib/logging/__init__.py b/Lib/logging/__init__.py
index 83db827..19b96b8 100644
--- a/Lib/logging/__init__.py
+++ b/Lib/logging/__init__.py
@@ -37,10 +37,7 @@ __all__ = ['BASIC_FORMAT', 'BufferingFormatter', 'CRITICAL', 'DEBUG', 'ERROR',
            'warn', 'warning', 'getLogRecordFactory', 'setLogRecordFactory',
            'lastResort', 'raiseExceptions']
 
-try:
-    import threading
-except ImportError: #pragma: no cover
-    threading = None
+import threading
 
 __author__  = "Vinay Sajip <vinay_sajip@red-dove.com>"
 __status__  = "production"
@@ -210,11 +207,7 @@ def _checkLevel(level):
 #the lock would already have been acquired - so we need an RLock.
 #The same argument applies to Loggers and Manager.loggerDict.
 #
-if threading:
-    _lock = threading.RLock()
-else: #pragma: no cover
-    _lock = None
-
+_lock = threading.RLock()
 
 def _acquireLock():
     """
@@ -295,7 +288,7 @@ class LogRecord(object):
         self.created = ct
         self.msecs = (ct - int(ct)) * 1000
         self.relativeCreated = (self.created - _startTime) * 1000
-        if logThreads and threading:
+        if logThreads:
             self.thread = threading.get_ident()
             self.threadName = threading.current_thread().name
         else: # pragma: no cover
@@ -799,10 +792,7 @@ class Handler(Filterer):
         """
         Acquire a thread lock for serializing access to the underlying I/O.
         """
-        if threading:
-            self.lock = threading.RLock()
-        else: #pragma: no cover
-            self.lock = None
+        self.lock = threading.RLock()
 
     def acquire(self):
         """
diff --git a/Lib/logging/config.py b/Lib/logging/config.py
index b3f4e28..c16a75a 100644
--- a/Lib/logging/config.py
+++ b/Lib/logging/config.py
@@ -31,14 +31,9 @@ import logging.handlers
 import re
 import struct
 import sys
+import threading
 import traceback
 
-try:
-    import _thread as thread
-    import threading
-except ImportError: #pragma: no cover
-    thread = None
-
 from socketserver import ThreadingTCPServer, StreamRequestHandler
 
 
@@ -816,8 +811,6 @@ def listen(port=DEFAULT_LOGGING_CONFIG_PORT, verify=None):
     normal. Note that you can return transformed bytes, e.g. by decrypting
     the bytes passed in.
     """
-    if not thread: #pragma: no cover
-        raise NotImplementedError("listen() needs threading to work")
 
     class ConfigStreamHandler(StreamRequestHandler):
         """
diff --git a/Lib/logging/handlers.py b/Lib/logging/handlers.py
index b5fdfbc..a815f03 100644
--- a/Lib/logging/handlers.py
+++ b/Lib/logging/handlers.py
@@ -26,10 +26,7 @@ To use, simply 'import logging.handlers' and log away!
 import logging, socket, os, pickle, struct, time, re
 from stat import ST_DEV, ST_INO, ST_MTIME
 import queue
-try:
-    import threading
-except ImportError: #pragma: no cover
-    threading = None
+import threading
 
 #
 # Some constants...
@@ -1395,110 +1392,110 @@ class QueueHandler(logging.Handler):
         except Exception:
             self.handleError(record)
 
-if threading:
-    class QueueListener(object):
-        """
-        This class implements an internal threaded listener which watches for
-        LogRecords being added to a queue, removes them and passes them to a
-        list of handlers for processing.
-        """
-        _sentinel = None
-
-        def __init__(self, queue, *handlers, respect_handler_level=False):
-            """
-            Initialise an instance with the specified queue and
-            handlers.
-            """
-            self.queue = queue
-            self.handlers = handlers
-            self._thread = None
-            self.respect_handler_level = respect_handler_level
-
-        def dequeue(self, block):
-            """
-            Dequeue a record and return it, optionally blocking.
-
-            The base implementation uses get. You may want to override this method
-            if you want to use timeouts or work with custom queue implementations.
-            """
-            return self.queue.get(block)
-
-        def start(self):
-            """
-            Start the listener.
-
-            This starts up a background thread to monitor the queue for
-            LogRecords to process.
-            """
-            self._thread = t = threading.Thread(target=self._monitor)
-            t.daemon = True
-            t.start()
-
-        def prepare(self , record):
-            """
-            Prepare a record for handling.
-
-            This method just returns the passed-in record. You may want to
-            override this method if you need to do any custom marshalling or
-            manipulation of the record before passing it to the handlers.
-            """
-            return record
-
-        def handle(self, record):
-            """
-            Handle a record.
-
-            This just loops through the handlers offering them the record
-            to handle.
-            """
-            record = self.prepare(record)
-            for handler in self.handlers:
-                if not self.respect_handler_level:
-                    process = True
-                else:
-                    process = record.levelno >= handler.level
-                if process:
-                    handler.handle(record)
-
-        def _monitor(self):
-            """
-            Monitor the queue for records, and ask the handler
-            to deal with them.
-
-            This method runs on a separate, internal thread.
-            The thread will terminate if it sees a sentinel object in the queue.
-            """
-            q = self.queue
-            has_task_done = hasattr(q, 'task_done')
-            while True:
-                try:
-                    record = self.dequeue(True)
-                    if record is self._sentinel:
-                        break
-                    self.handle(record)
-                    if has_task_done:
-                        q.task_done()
-                except queue.Empty:
+
+class QueueListener(object):
+    """
+    This class implements an internal threaded listener which watches for
+    LogRecords being added to a queue, removes them and passes them to a
+    list of handlers for processing.
+    """
+    _sentinel = None
+
+    def __init__(self, queue, *handlers, respect_handler_level=False):
+        """
+        Initialise an instance with the specified queue and
+        handlers.
+        """
+        self.queue = queue
+        self.handlers = handlers
+        self._thread = None
+        self.respect_handler_level = respect_handler_level
+
+    def dequeue(self, block):
+        """
+        Dequeue a record and return it, optionally blocking.
+
+        The base implementation uses get. You may want to override this method
+        if you want to use timeouts or work with custom queue implementations.
+        """
+        return self.queue.get(block)
+
+    def start(self):
+        """
+        Start the listener.
+
+        This starts up a background thread to monitor the queue for
+        LogRecords to process.
+        """
+        self._thread = t = threading.Thread(target=self._monitor)
+        t.daemon = True
+        t.start()
+
+    def prepare(self , record):
+        """
+        Prepare a record for handling.
+
+        This method just returns the passed-in record. You may want to
+        override this method if you need to do any custom marshalling or
+        manipulation of the record before passing it to the handlers.
+        """
+        return record
+
+    def handle(self, record):
+        """
+        Handle a record.
+
+        This just loops through the handlers offering them the record
+        to handle.
+        """
+        record = self.prepare(record)
+        for handler in self.handlers:
+            if not self.respect_handler_level:
+                process = True
+            else:
+                process = record.levelno >= handler.level
+            if process:
+                handler.handle(record)
+
+    def _monitor(self):
+        """
+        Monitor the queue for records, and ask the handler
+        to deal with them.
+
+        This method runs on a separate, internal thread.
+        The thread will terminate if it sees a sentinel object in the queue.
+        """
+        q = self.queue
+        has_task_done = hasattr(q, 'task_done')
+        while True:
+            try:
+                record = self.dequeue(True)
+                if record is self._sentinel:
                     break
+                self.handle(record)
+                if has_task_done:
+                    q.task_done()
+            except queue.Empty:
+                break
+
+    def enqueue_sentinel(self):
+        """
+        This is used to enqueue the sentinel record.
+
+        The base implementation uses put_nowait. You may want to override this
+        method if you want to use timeouts or work with custom queue
+        implementations.
+        """
+        self.queue.put_nowait(self._sentinel)
 
-        def enqueue_sentinel(self):
-            """
-            This is used to enqueue the sentinel record.
-
-            The base implementation uses put_nowait. You may want to override this
-            method if you want to use timeouts or work with custom queue
-            implementations.
-            """
-            self.queue.put_nowait(self._sentinel)
-
-        def stop(self):
-            """
-            Stop the listener.
-
-            This asks the thread to terminate, and then waits for it to do so.
-            Note that if you don't call this before your application exits, there
-            may be some records still left on the queue, which won't be processed.
-            """
-            self.enqueue_sentinel()
-            self._thread.join()
-            self._thread = None
+    def stop(self):
+        """
+        Stop the listener.
+
+        This asks the thread to terminate, and then waits for it to do so.
+        Note that if you don't call this before your application exits, there
+        may be some records still left on the queue, which won't be processed.
+        """
+        self.enqueue_sentinel()
+        self._thread.join()
+        self._thread = None
diff --git a/Lib/queue.py b/Lib/queue.py
index 572425e..c803b96 100644
--- a/Lib/queue.py
+++ b/Lib/queue.py
@@ -1,9 +1,6 @@
 '''A multi-producer, multi-consumer queue.'''
 
-try:
-    import threading
-except ImportError:
-    import dummy_threading as threading
+import threading
 from collections import deque
 from heapq import heappush, heappop
 from time import monotonic as time
diff --git a/Lib/reprlib.py b/Lib/reprlib.py
index 40d991f..616b343 100644
--- a/Lib/reprlib.py
+++ b/Lib/reprlib.py
@@ -4,10 +4,7 @@ __all__ = ["Repr", "repr", "recursive_repr"]
 
 import builtins
 from itertools import islice
-try:
-    from _thread import get_ident
-except ImportError:
-    from _dummy_thread import get_ident
+from _thread import get_ident
 
 def recursive_repr(fillvalue='...'):
     'Decorator to make a repr function return fillvalue for a recursive call'
diff --git a/Lib/sched.py b/Lib/sched.py
index 3d8c011..ff87874 100644
--- a/Lib/sched.py
+++ b/Lib/sched.py
@@ -26,10 +26,7 @@ has another way to reference private data (besides global variables).
 import time
 import heapq
 from collections import namedtuple
-try:
-    import threading
-except ImportError:
-    import dummy_threading as threading
+import threading
 from time import monotonic as _time
 
 __all__ = ["scheduler"]
diff --git a/Lib/socketserver.py b/Lib/socketserver.py
index df17114..721eb50 100644
--- a/Lib/socketserver.py
+++ b/Lib/socketserver.py
@@ -127,10 +127,7 @@ import socket
 import selectors
 import os
 import sys
-try:
-    import threading
-except ImportError:
-    import dummy_threading as threading
+import threading
 from io import BufferedIOBase
 from time import monotonic as time
 
diff --git a/Lib/sqlite3/test/dbapi.py b/Lib/sqlite3/test/dbapi.py
index cb85814..12c9fb4 100644
--- a/Lib/sqlite3/test/dbapi.py
+++ b/Lib/sqlite3/test/dbapi.py
@@ -21,12 +21,9 @@
 #    misrepresented as being the original software.
 # 3. This notice may not be removed or altered from any source distribution.
 
+import threading
 import unittest
 import sqlite3 as sqlite
-try:
-    import threading
-except ImportError:
-    threading = None
 
 from test.support import TESTFN, unlink
 
@@ -503,7 +500,6 @@ class CursorTests(unittest.TestCase):
         self.assertEqual(results, expected)
 
 
-@unittest.skipUnless(threading, 'This test requires threading.')
 class ThreadTests(unittest.TestCase):
     def setUp(self):
         self.con = sqlite.connect(":memory:")
diff --git a/Lib/subprocess.py b/Lib/subprocess.py
index 25e5698..f61ff0c 100644
--- a/Lib/subprocess.py
+++ b/Lib/subprocess.py
@@ -138,10 +138,7 @@ else:
     import _posixsubprocess
     import select
     import selectors
-    try:
-        import threading
-    except ImportError:
-        import dummy_threading as threading
+    import threading
 
     # When select or poll has indicated that the file is writable,
     # we can write up to _PIPE_BUF bytes without risk of blocking.
diff --git a/Lib/tempfile.py b/Lib/tempfile.py
index 6146235..71ecafa 100644
--- a/Lib/tempfile.py
+++ b/Lib/tempfile.py
@@ -44,11 +44,7 @@ import shutil as _shutil
 import errno as _errno
 from random import Random as _Random
 import weakref as _weakref
-
-try:
-    import _thread
-except ImportError:
-    import _dummy_thread as _thread
+import _thread
 _allocate_lock = _thread.allocate_lock
 
 _text_openflags = _os.O_RDWR | _os.O_CREAT | _os.O_EXCL
diff --git a/Lib/test/fork_wait.py b/Lib/test/fork_wait.py
index 6af79ad..9850b06 100644
--- a/Lib/test/fork_wait.py
+++ b/Lib/test/fork_wait.py
@@ -10,9 +10,9 @@ active threads survive in the child after a fork(); this is an error.
 """
 
 import os, sys, time, unittest
+import threading
 import test.support as support
 
-threading = support.import_module('threading')
 
 LONGSLEEP = 2
 SHORTSLEEP = 0.5
diff --git a/Lib/test/libregrtest/runtest_mp.py b/Lib/test/libregrtest/runtest_mp.py
index 779ff01..31b830d 100644
--- a/Lib/test/libregrtest/runtest_mp.py
+++ b/Lib/test/libregrtest/runtest_mp.py
@@ -3,15 +3,11 @@ import json
 import os
 import queue
 import sys
+import threading
 import time
 import traceback
 import types
 from test import support
-try:
-    import threading
-except ImportError:
-    print("Multiprocess option requires thread support")
-    sys.exit(2)
 
 from test.libregrtest.runtest import (
     runtest, INTERRUPTED, CHILD_ERROR, PROGRESS_MIN_TIME,
diff --git a/Lib/test/libregrtest/save_env.py b/Lib/test/libregrtest/save_env.py
index 3c45621..45b365d 100644
--- a/Lib/test/libregrtest/save_env.py
+++ b/Lib/test/libregrtest/save_env.py
@@ -5,13 +5,10 @@ import os
 import shutil
 import sys
 import sysconfig
+import threading
 import warnings
 from test import support
 try:
-    import threading
-except ImportError:
-    threading = None
-try:
     import _multiprocessing, multiprocessing.process
 except ImportError:
     multiprocessing = None
@@ -181,13 +178,9 @@ class saved_test_environment:
     # Controlling dangling references to Thread objects can make it easier
     # to track reference leaks.
     def get_threading__dangling(self):
-        if not threading:
-            return None
         # This copies the weakrefs without making any strong reference
         return threading._dangling.copy()
     def restore_threading__dangling(self, saved):
-        if not threading:
-            return
         threading._dangling.clear()
         threading._dangling.update(saved)
 
diff --git a/Lib/test/support/__init__.py b/Lib/test/support/__init__.py
index 0235498..bfceba1 100644
--- a/Lib/test/support/__init__.py
+++ b/Lib/test/support/__init__.py
@@ -25,6 +25,8 @@ import subprocess
 import sys
 import sysconfig
 import tempfile
+import _thread
+import threading
 import time
 import types
 import unittest
@@ -32,11 +34,6 @@ import urllib.error
 import warnings
 
 try:
-    import _thread, threading
-except ImportError:
-    _thread = None
-    threading = None
-try:
     import multiprocessing.process
 except ImportError:
     multiprocessing = None
@@ -2028,16 +2025,11 @@ environment_altered = False
 # at the end of a test run.
 
 def threading_setup():
-    if _thread:
-        return _thread._count(), threading._dangling.copy()
-    else:
-        return 1, ()
+    return _thread._count(), threading._dangling.copy()
 
 def threading_cleanup(*original_values):
     global environment_altered
 
-    if not _thread:
-        return
     _MAX_COUNT = 100
     t0 = time.monotonic()
     for count in range(_MAX_COUNT):
@@ -2061,9 +2053,6 @@ def reap_threads(func):
     ensure that the threads are cleaned up even when the test fails.
     If threading is unavailable this function does nothing.
     """
-    if not _thread:
-        return func
-
     @functools.wraps(func)
     def decorator(*args):
         key = threading_setup()
diff --git a/Lib/test/test_asynchat.py b/Lib/test/test_asynchat.py
index 0eba76d..2362834 100644
--- a/Lib/test/test_asynchat.py
+++ b/Lib/test/test_asynchat.py
@@ -2,110 +2,104 @@
 
 from test import support
 
-# If this fails, the test will be skipped.
-thread = support.import_module('_thread')
-
 import asynchat
 import asyncore
 import errno
 import socket
 import sys
+import _thread as thread
+import threading
 import time
 import unittest
 import unittest.mock
-try:
-    import threading
-except ImportError:
-    threading = None
 
 HOST = support.HOST
 SERVER_QUIT = b'QUIT\n'
 TIMEOUT = 3.0
 
-if threading:
-    class echo_server(threading.Thread):
-        # parameter to determine the number of bytes passed back to the
-        # client each send
-        chunk_size = 1
-
-        def __init__(self, event):
-            threading.Thread.__init__(self)
-            self.event = event
-            self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
-            self.port = support.bind_port(self.sock)
-            # This will be set if the client wants us to wait before echoing
-            # data back.
-            self.start_resend_event = None
-
-        def run(self):
-            self.sock.listen()
-            self.event.set()
-            conn, client = self.sock.accept()
-            self.buffer = b""
-            # collect data until quit message is seen
-            while SERVER_QUIT not in self.buffer:
-                data = conn.recv(1)
-                if not data:
-                    break
-                self.buffer = self.buffer + data
-
-            # remove the SERVER_QUIT message
-            self.buffer = self.buffer.replace(SERVER_QUIT, b'')
-
-            if self.start_resend_event:
-                self.start_resend_event.wait()
-
-            # re-send entire set of collected data
-            try:
-                # this may fail on some tests, such as test_close_when_done,
-                # since the client closes the channel when it's done sending
-                while self.buffer:
-                    n = conn.send(self.buffer[:self.chunk_size])
-                    time.sleep(0.001)
-                    self.buffer = self.buffer[n:]
-            except:
-                pass
-
-            conn.close()
-            self.sock.close()
 
-    class echo_client(asynchat.async_chat):
-
-        def __init__(self, terminator, server_port):
-            asynchat.async_chat.__init__(self)
-            self.contents = []
-            self.create_socket(socket.AF_INET, socket.SOCK_STREAM)
-            self.connect((HOST, server_port))
-            self.set_terminator(terminator)
-            self.buffer = b""
-
-            def handle_connect(self):
+class echo_server(threading.Thread):
+    # parameter to determine the number of bytes passed back to the
+    # client each send
+    chunk_size = 1
+
+    def __init__(self, event):
+        threading.Thread.__init__(self)
+        self.event = event
+        self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+        self.port = support.bind_port(self.sock)
+        # This will be set if the client wants us to wait before echoing
+        # data back.
+        self.start_resend_event = None
+
+    def run(self):
+        self.sock.listen()
+        self.event.set()
+        conn, client = self.sock.accept()
+        self.buffer = b""
+        # collect data until quit message is seen
+        while SERVER_QUIT not in self.buffer:
+            data = conn.recv(1)
+            if not data:
+                break
+            self.buffer = self.buffer + data
+
+        # remove the SERVER_QUIT message
+        self.buffer = self.buffer.replace(SERVER_QUIT, b'')
+
+        if self.start_resend_event:
+            self.start_resend_event.wait()
+
+        # re-send entire set of collected data
+        try:
+            # this may fail on some tests, such as test_close_when_done,
+            # since the client closes the channel when it's done sending
+            while self.buffer:
+                n = conn.send(self.buffer[:self.chunk_size])
+                time.sleep(0.001)
+                self.buffer = self.buffer[n:]
+        except:
+            pass
+
+        conn.close()
+        self.sock.close()
+
+class echo_client(asynchat.async_chat):
+
+    def __init__(self, terminator, server_port):
+        asynchat.async_chat.__init__(self)
+        self.contents = []
+        self.create_socket(socket.AF_INET, socket.SOCK_STREAM)
+        self.connect((HOST, server_port))
+        self.set_terminator(terminator)
+        self.buffer = b""
+
+        def handle_connect(self):
+            pass
+
+        if sys.platform == 'darwin':
+            # select.poll returns a select.POLLHUP at the end of the tests
+            # on darwin, so just ignore it
+            def handle_expt(self):
                 pass
 
-            if sys.platform == 'darwin':
-                # select.poll returns a select.POLLHUP at the end of the tests
-                # on darwin, so just ignore it
-                def handle_expt(self):
-                    pass
-
-        def collect_incoming_data(self, data):
-            self.buffer += data
+    def collect_incoming_data(self, data):
+        self.buffer += data
 
-        def found_terminator(self):
-            self.contents.append(self.buffer)
-            self.buffer = b""
+    def found_terminator(self):
+        self.contents.append(self.buffer)
+        self.buffer = b""
 
-    def start_echo_server():
-        event = threading.Event()
-        s = echo_server(event)
-        s.start()
-        event.wait()
-        event.clear()
-        time.sleep(0.01)   # Give server time to start accepting.
-        return s, event
+def start_echo_server():
+    event = threading.Event()
+    s = echo_server(event)
+    s.start()
+    event.wait()
+    event.clear()
+    time.sleep(0.01)   # Give server time to start accepting.
+    return s, event
 
 
-@unittest.skipUnless(threading, 'Threading required for this test.')
 class TestAsynchat(unittest.TestCase):
     usepoll = False
 
diff --git a/Lib/test/test_asyncio/__init__.py b/Lib/test/test_asyncio/__init__.py
index 80a9eea..c77c7a8 100644
--- a/Lib/test/test_asyncio/__init__.py
+++ b/Lib/test/test_asyncio/__init__.py
@@ -1,8 +1,6 @@
 import os
 from test.support import load_package_tests, import_module
 
-# Skip tests if we don't have threading.
-import_module('threading')
 # Skip tests if we don't have concurrent.futures.
 import_module('concurrent.futures')
 
diff --git a/Lib/test/test_asyncore.py b/Lib/test/test_asyncore.py
index 07edf22..c8e9727 100644
--- a/Lib/test/test_asyncore.py
+++ b/Lib/test/test_asyncore.py
@@ -7,6 +7,7 @@ import sys
 import time
 import errno
 import struct
+import threading
 
 from test import support
 from io import BytesIO
@@ -14,10 +15,6 @@ from io import BytesIO
 if support.PGO:
     raise unittest.SkipTest("test is not helpful for PGO")
 
-try:
-    import threading
-except ImportError:
-    threading = None
 
 TIMEOUT = 3
 HAS_UNIX_SOCKETS = hasattr(socket, 'AF_UNIX')
@@ -326,7 +323,6 @@ class DispatcherWithSendTests(unittest.TestCase):
     def tearDown(self):
         asyncore.close_all()
 
-    @unittest.skipUnless(threading, 'Threading required for this test.')
     @support.reap_threads
     def test_send(self):
         evt = threading.Event()
@@ -776,7 +772,6 @@ class BaseTestAPI:
                 self.assertTrue(s.socket.getsockopt(socket.SOL_SOCKET,
                                                      socket.SO_REUSEADDR))
 
-    @unittest.skipUnless(threading, 'Threading required for this test.')
     @support.reap_threads
     def test_quick_connect(self):
         # see: http://bugs.python.org/issue10340
diff --git a/Lib/test/test_bz2.py b/Lib/test/test_bz2.py
index e76b283..58dbf96 100644
--- a/Lib/test/test_bz2.py
+++ b/Lib/test/test_bz2.py
@@ -10,13 +10,10 @@ import pathlib
 import random
 import shutil
 import subprocess
+import threading
 from test.support import unlink
 import _compression
 
-try:
-    import threading
-except ImportError:
-    threading = None
 
 # Skip tests if the bz2 module doesn't exist.
 bz2 = support.import_module('bz2')
@@ -491,7 +488,6 @@ class BZ2FileTest(BaseTest):
         else:
             self.fail("1/0 didn't raise an exception")
 
-    @unittest.skipUnless(threading, 'Threading required for this test.')
     def testThreading(self):
         # Issue #7205: Using a BZ2File from several threads shouldn't deadlock.
         data = b"1" * 2**20
@@ -504,13 +500,6 @@ class BZ2FileTest(BaseTest):
             with support.start_threads(threads):
                 pass
 
-    def testWithoutThreading(self):
-        module = support.import_fresh_module("bz2", blocked=("threading",))
-        with module.BZ2File(self.filename, "wb") as f:
-            f.write(b"abc")
-        with module.BZ2File(self.filename, "rb") as f:
-            self.assertEqual(f.read(), b"abc")
-
     def testMixedIterationAndReads(self):
         self.createTempFile()
         linelen = len(self.TEXT_LINES[0])
diff --git a/Lib/test/test_capi.py b/Lib/test/test_capi.py
index c3a04b4..1b826ee 100644
--- a/Lib/test/test_capi.py
+++ b/Lib/test/test_capi.py
@@ -11,6 +11,7 @@ import subprocess
 import sys
 import sysconfig
 import textwrap
+import threading
 import time
 import unittest
 from test import support
@@ -20,10 +21,7 @@ try:
     import _posixsubprocess
 except ImportError:
     _posixsubprocess = None
-try:
-    import threading
-except ImportError:
-    threading = None
+
 # Skip this test if the _testcapi module isn't available.
 _testcapi = support.import_module('_testcapi')
 
@@ -52,7 +50,6 @@ class CAPITest(unittest.TestCase):
         self.assertEqual(testfunction.attribute, "test")
         self.assertRaises(AttributeError, setattr, inst.testfunction, "attribute", "test")
 
-    @unittest.skipUnless(threading, 'Threading required for this test.')
     def test_no_FatalError_infinite_loop(self):
         with support.SuppressCrashReport():
             p = subprocess.Popen([sys.executable, "-c",
@@ -276,7 +273,6 @@ class CAPITest(unittest.TestCase):
         self.assertIn(b'MemoryError 3 30', out)
 
 
-@unittest.skipUnless(threading, 'Threading required for this test.')
 class TestPendingCalls(unittest.TestCase):
 
     def pendingcalls_submit(self, l, n):
@@ -685,7 +681,6 @@ class SkipitemTest(unittest.TestCase):
             parse((1,), {}, 'O|OO', ['', 'a', ''])
 
 
-@unittest.skipUnless(threading, 'Threading required for this test.')
 class TestThreadState(unittest.TestCase):
 
     @support.reap_threads
@@ -762,7 +757,6 @@ class PyMemDebugTests(unittest.TestCase):
         regex = regex.format(ptr=self.PTR_REGEX)
         self.assertRegex(out, regex)
 
-    @unittest.skipUnless(threading, 'Test requires a GIL (multithreading)')
     def check_malloc_without_gil(self, code):
         out = self.check(code)
         expected = ('Fatal Python error: Python memory allocator called '
diff --git a/Lib/test/test_concurrent_futures.py b/Lib/test/test_concurrent_futures.py
index 03f8d1d..a888dca 100644
--- a/Lib/test/test_concurrent_futures.py
+++ b/Lib/test/test_concurrent_futures.py
@@ -4,10 +4,6 @@ import test.support
 test.support.import_module('_multiprocessing')
 # Skip tests if sem_open implementation is broken.
 test.support.import_module('multiprocessing.synchronize')
-# import threading after _multiprocessing to raise a more relevant error
-# message: "No module named _multiprocessing". _multiprocessing is not compiled
-# without thread support.
-test.support.import_module('threading')
 
 from test.support.script_helper import assert_python_ok
 
diff --git a/Lib/test/test_contextlib.py b/Lib/test/test_contextlib.py
index 2301f75..64b6578 100644
--- a/Lib/test/test_contextlib.py
+++ b/Lib/test/test_contextlib.py
@@ -3,13 +3,10 @@
 import io
 import sys
 import tempfile
+import threading
 import unittest
 from contextlib import *  # Tests __all__
 from test import support
-try:
-    import threading
-except ImportError:
-    threading = None
 
 
 class TestAbstractContextManager(unittest.TestCase):
@@ -275,7 +272,6 @@ class FileContextTestCase(unittest.TestCase):
         finally:
             support.unlink(tfn)
 
-@unittest.skipUnless(threading, 'Threading required for this test.')
 class LockContextTestCase(unittest.TestCase):
 
     def boilerPlate(self, lock, locked):
diff --git a/Lib/test/test_decimal.py b/Lib/test/test_decimal.py
index 53f71ca..5d9da0e 100644
--- a/Lib/test/test_decimal.py
+++ b/Lib/test/test_decimal.py
@@ -38,10 +38,7 @@ from test.support import (import_fresh_module, TestFailed,
                           run_with_locale, cpython_only)
 import random
 import inspect
-try:
-    import threading
-except ImportError:
-    threading = None
+import threading
 
 
 C = import_fresh_module('decimal', fresh=['_decimal'])
@@ -1625,10 +1622,10 @@ class ThreadingTest(unittest.TestCase):
         DefaultContext.Emax = save_emax
         DefaultContext.Emin = save_emin
 
-@unittest.skipUnless(threading, 'threading required')
+
 class CThreadingTest(ThreadingTest):
     decimal = C
-@unittest.skipUnless(threading, 'threading required')
+
 class PyThreadingTest(ThreadingTest):
     decimal = P
 
diff --git a/Lib/test/test_docxmlrpc.py b/Lib/test/test_docxmlrpc.py
index 0090333..f077f05 100644
--- a/Lib/test/test_docxmlrpc.py
+++ b/Lib/test/test_docxmlrpc.py
@@ -1,8 +1,8 @@
 from xmlrpc.server import DocXMLRPCServer
 import http.client
 import sys
+import threading
 from test import support
-threading = support.import_module('threading')
 import unittest
 
 def make_request_and_skipIf(condition, reason):
diff --git a/Lib/test/test_dummy_thread.py b/Lib/test/test_dummy_thread.py
deleted file mode 100644
index 0840be6..0000000
--- a/Lib/test/test_dummy_thread.py
+++ /dev/null
@@ -1,255 +0,0 @@
-import _dummy_thread as _thread
-import time
-import queue
-import random
-import unittest
-from test import support
-from unittest import mock
-
-DELAY = 0
-
-
-class LockTests(unittest.TestCase):
-    """Test lock objects."""
-
-    def setUp(self):
-        # Create a lock
-        self.lock = _thread.allocate_lock()
-
-    def test_initlock(self):
-        #Make sure locks start locked
-        self.assertFalse(self.lock.locked(),
-                        "Lock object is not initialized unlocked.")
-
-    def test_release(self):
-        # Test self.lock.release()
-        self.lock.acquire()
-        self.lock.release()
-        self.assertFalse(self.lock.locked(),
-                        "Lock object did not release properly.")
-
-    def test_LockType_context_manager(self):
-        with _thread.LockType():
-            pass
-        self.assertFalse(self.lock.locked(),
-                         "Acquired Lock was not released")
-
-    def test_improper_release(self):
-        #Make sure release of an unlocked thread raises RuntimeError
-        self.assertRaises(RuntimeError, self.lock.release)
-
-    def test_cond_acquire_success(self):
-        #Make sure the conditional acquiring of the lock works.
-        self.assertTrue(self.lock.acquire(0),
-                        "Conditional acquiring of the lock failed.")
-
-    def test_cond_acquire_fail(self):
-        #Test acquiring locked lock returns False
-        self.lock.acquire(0)
-        self.assertFalse(self.lock.acquire(0),
-                        "Conditional acquiring of a locked lock incorrectly "
-                         "succeeded.")
-
-    def test_uncond_acquire_success(self):
-        #Make sure unconditional acquiring of a lock works.
-        self.lock.acquire()
-        self.assertTrue(self.lock.locked(),
-                        "Uncondional locking failed.")
-
-    def test_uncond_acquire_return_val(self):
-        #Make sure that an unconditional locking returns True.
-        self.assertIs(self.lock.acquire(1), True,
-                        "Unconditional locking did not return True.")
-        self.assertIs(self.lock.acquire(), True)
-
-    def test_uncond_acquire_blocking(self):
-        #Make sure that unconditional acquiring of a locked lock blocks.
-        def delay_unlock(to_unlock, delay):
-            """Hold on to lock for a set amount of time before unlocking."""
-            time.sleep(delay)
-            to_unlock.release()
-
-        self.lock.acquire()
-        start_time = int(time.time())
-        _thread.start_new_thread(delay_unlock,(self.lock, DELAY))
-        if support.verbose:
-            print()
-            print("*** Waiting for thread to release the lock "\
-            "(approx. %s sec.) ***" % DELAY)
-        self.lock.acquire()
-        end_time = int(time.time())
-        if support.verbose:
-            print("done")
-        self.assertGreaterEqual(end_time - start_time, DELAY,
-                        "Blocking by unconditional acquiring failed.")
-
-    @mock.patch('time.sleep')
-    def test_acquire_timeout(self, mock_sleep):
-        """Test invoking acquire() with a positive timeout when the lock is
-        already acquired. Ensure that time.sleep() is invoked with the given
-        timeout and that False is returned."""
-
-        self.lock.acquire()
-        retval = self.lock.acquire(waitflag=0, timeout=1)
-        self.assertTrue(mock_sleep.called)
-        mock_sleep.assert_called_once_with(1)
-        self.assertEqual(retval, False)
-
-    def test_lock_representation(self):
-        self.lock.acquire()
-        self.assertIn("locked", repr(self.lock))
-        self.lock.release()
-        self.assertIn("unlocked", repr(self.lock))
-
-
-class MiscTests(unittest.TestCase):
-    """Miscellaneous tests."""
-
-    def test_exit(self):
-        self.assertRaises(SystemExit, _thread.exit)
-
-    def test_ident(self):
-        self.assertIsInstance(_thread.get_ident(), int,
-                              "_thread.get_ident() returned a non-integer")
-        self.assertGreater(_thread.get_ident(), 0)
-
-    def test_LockType(self):
-        self.assertIsInstance(_thread.allocate_lock(), _thread.LockType,
-                              "_thread.LockType is not an instance of what "
-                              "is returned by _thread.allocate_lock()")
-
-    def test_set_sentinel(self):
-        self.assertIsInstance(_thread._set_sentinel(), _thread.LockType,
-                              "_thread._set_sentinel() did not return a "
-                              "LockType instance.")
-
-    def test_interrupt_main(self):
-        #Calling start_new_thread with a function that executes interrupt_main
-        # should raise KeyboardInterrupt upon completion.
-        def call_interrupt():
-            _thread.interrupt_main()
-
-        self.assertRaises(KeyboardInterrupt,
-                          _thread.start_new_thread,
-                          call_interrupt,
-                          tuple())
-
-    def test_interrupt_in_main(self):
-        self.assertRaises(KeyboardInterrupt, _thread.interrupt_main)
-
-    def test_stack_size_None(self):
-        retval = _thread.stack_size(None)
-        self.assertEqual(retval, 0)
-
-    def test_stack_size_not_None(self):
-        with self.assertRaises(_thread.error) as cm:
-            _thread.stack_size("")
-        self.assertEqual(cm.exception.args[0],
-                         "setting thread stack size not supported")
-
-
-class ThreadTests(unittest.TestCase):
-    """Test thread creation."""
-
-    def test_arg_passing(self):
-        #Make sure that parameter passing works.
-        def arg_tester(queue, arg1=False, arg2=False):
-            """Use to test _thread.start_new_thread() passes args properly."""
-            queue.put((arg1, arg2))
-
-        testing_queue = queue.Queue(1)
-        _thread.start_new_thread(arg_tester, (testing_queue, True, True))
-        result = testing_queue.get()
-        self.assertTrue(result[0] and result[1],
-                        "Argument passing for thread creation "
-                        "using tuple failed")
-
-        _thread.start_new_thread(
-                arg_tester,
-                tuple(),
-                {'queue':testing_queue, 'arg1':True, 'arg2':True})
-
-        result = testing_queue.get()
-        self.assertTrue(result[0] and result[1],
-                        "Argument passing for thread creation "
-                        "using kwargs failed")
-
-        _thread.start_new_thread(
-                arg_tester,
-                (testing_queue, True),
-                {'arg2':True})
-
-        result = testing_queue.get()
-        self.assertTrue(result[0] and result[1],
-                        "Argument passing for thread creation using both tuple"
-                        " and kwargs failed")
-
-    def test_multi_thread_creation(self):
-        def queue_mark(queue, delay):
-            time.sleep(delay)
-            queue.put(_thread.get_ident())
-
-        thread_count = 5
-        testing_queue = queue.Queue(thread_count)
-
-        if support.verbose:
-            print()
-            print("*** Testing multiple thread creation "
-                  "(will take approx. %s to %s sec.) ***" % (
-                    DELAY, thread_count))
-
-        for count in range(thread_count):
-            if DELAY:
-                local_delay = round(random.random(), 1)
-            else:
-                local_delay = 0
-            _thread.start_new_thread(queue_mark,
-                                     (testing_queue, local_delay))
-        time.sleep(DELAY)
-        if support.verbose:
-            print('done')
-        self.assertEqual(testing_queue.qsize(), thread_count,
-                         "Not all %s threads executed properly "
-                         "after %s sec." % (thread_count, DELAY))
-
-    def test_args_not_tuple(self):
-        """
-        Test invoking start_new_thread() with a non-tuple value for "args".
-        Expect TypeError with a meaningful error message to be raised.
-        """
-        with self.assertRaises(TypeError) as cm:
-            _thread.start_new_thread(mock.Mock(), [])
-        self.assertEqual(cm.exception.args[0], "2nd arg must be a tuple")
-
-    def test_kwargs_not_dict(self):
-        """
-        Test invoking start_new_thread() with a non-dict value for "kwargs".
-        Expect TypeError with a meaningful error message to be raised.
-        """
-        with self.assertRaises(TypeError) as cm:
-            _thread.start_new_thread(mock.Mock(), tuple(), kwargs=[])
-        self.assertEqual(cm.exception.args[0], "3rd arg must be a dict")
-
-    def test_SystemExit(self):
-        """
-        Test invoking start_new_thread() with a function that raises
-        SystemExit.
-        The exception should be discarded.
-        """
-        func = mock.Mock(side_effect=SystemExit())
-        try:
-            _thread.start_new_thread(func, tuple())
-        except SystemExit:
-            self.fail("start_new_thread raised SystemExit.")
-
-    @mock.patch('traceback.print_exc')
-    def test_RaiseException(self, mock_print_exc):
-        """
-        Test invoking start_new_thread() with a function that raises exception.
-
-        The exception should be discarded and the traceback should be printed
-        via traceback.print_exc()
-        """
-        func = mock.Mock(side_effect=Exception)
-        _thread.start_new_thread(func, tuple())
-        self.assertTrue(mock_print_exc.called)
diff --git a/Lib/test/test_dummy_threading.py b/Lib/test/test_dummy_threading.py
deleted file mode 100644
index a0c2972..0000000
--- a/Lib/test/test_dummy_threading.py
+++ /dev/null
@@ -1,60 +0,0 @@
-from test import support
-import unittest
-import dummy_threading as _threading
-import time
-
-class DummyThreadingTestCase(unittest.TestCase):
-
-    class TestThread(_threading.Thread):
-
-        def run(self):
-            global running
-            global sema
-            global mutex
-            # Uncomment if testing another module, such as the real 'threading'
-            # module.
-            #delay = random.random() * 2
-            delay = 0
-            if support.verbose:
-                print('task', self.name, 'will run for', delay, 'sec')
-            sema.acquire()
-            mutex.acquire()
-            running += 1
-            if support.verbose:
-                print(running, 'tasks are running')
-            mutex.release()
-            time.sleep(delay)
-            if support.verbose:
-                print('task', self.name, 'done')
-            mutex.acquire()
-            running -= 1
-            if support.verbose:
-                print(self.name, 'is finished.', running, 'tasks are running')
-            mutex.release()
-            sema.release()
-
-    def setUp(self):
-        self.numtasks = 10
-        global sema
-        sema = _threading.BoundedSemaphore(value=3)
-        global mutex
-        mutex = _threading.RLock()
-        global running
-        running = 0
-        self.threads = []
-
-    def test_tasks(self):
-        for i in range(self.numtasks):
-            t = self.TestThread(name="<thread %d>"%i)
-            self.threads.append(t)
-            t.start()
-
-        if support.verbose:
-            print('waiting for all tasks to complete')
-        for t in self.threads:
-            t.join()
-        if support.verbose:
-            print('all tasks done')
-
-if __name__ == '__main__':
-    unittest.main()
diff --git a/Lib/test/test_email/test_email.py b/Lib/test/test_email/test_email.py
index f97ccc6..621754c 100644
--- a/Lib/test/test_email/test_email.py
+++ b/Lib/test/test_email/test_email.py
@@ -12,10 +12,7 @@ from io import StringIO, BytesIO
 from itertools import chain
 from random import choice
 from socket import getfqdn
-try:
-    from threading import Thread
-except ImportError:
-    from dummy_threading import Thread
+from threading import Thread
 
 import email
 import email.policy
diff --git a/Lib/test/test_enum.py b/Lib/test/test_enum.py
index ea52de7..e6324d4 100644
--- a/Lib/test/test_enum.py
+++ b/Lib/test/test_enum.py
@@ -2,15 +2,12 @@ import enum
 import inspect
 import pydoc
 import unittest
+import threading
 from collections import OrderedDict
 from enum import Enum, IntEnum, EnumMeta, Flag, IntFlag, unique, auto
 from io import StringIO
 from pickle import dumps, loads, PicklingError, HIGHEST_PROTOCOL
 from test import support
-try:
-    import threading
-except ImportError:
-    threading = None
 
 
 # for pickle tests
@@ -1988,7 +1985,6 @@ class TestFlag(unittest.TestCase):
             d = 6
         self.assertEqual(repr(Bizarre(7)), '<Bizarre.d|c|b: 7>')
 
-    @unittest.skipUnless(threading, 'Threading required for this test.')
     @support.reap_threads
     def test_unique_composite(self):
         # override __eq__ to be identity only
@@ -2339,7 +2335,6 @@ class TestIntFlag(unittest.TestCase):
         for f in Open:
             self.assertEqual(bool(f.value), bool(f))
 
-    @unittest.skipUnless(threading, 'Threading required for this test.')
     @support.reap_threads
     def test_unique_composite(self):
         # override __eq__ to be identity only
diff --git a/Lib/test/test_faulthandler.py b/Lib/test/test_faulthandler.py
index e2fcb2b..889e641 100644
--- a/Lib/test/test_faulthandler.py
+++ b/Lib/test/test_faulthandler.py
@@ -8,15 +8,11 @@ import sys
 from test import support
 from test.support import script_helper, is_android, requires_android_level
 import tempfile
+import threading
 import unittest
 from textwrap import dedent
 
 try:
-    import threading
-    HAVE_THREADS = True
-except ImportError:
-    HAVE_THREADS = False
-try:
     import _testcapi
 except ImportError:
     _testcapi = None
@@ -154,7 +150,6 @@ class FaultHandlerTests(unittest.TestCase):
             3,
             'Segmentation fault')
 
-    @unittest.skipIf(not HAVE_THREADS, 'need threads')
     def test_fatal_error_c_thread(self):
         self.check_fatal_error("""
             import faulthandler
@@ -231,7 +226,7 @@ class FaultHandlerTests(unittest.TestCase):
             2,
             'xyz')
 
-    @unittest.skipIf(sys.platform.startswith('openbsd') and HAVE_THREADS,
+    @unittest.skipIf(sys.platform.startswith('openbsd'),
                      "Issue #12868: sigaltstack() doesn't work on "
                      "OpenBSD if Python is compiled with pthread")
     @unittest.skipIf(not hasattr(faulthandler, '_stack_overflow'),
@@ -456,7 +451,6 @@ class FaultHandlerTests(unittest.TestCase):
         self.assertEqual(trace, expected)
         self.assertEqual(exitcode, 0)
 
-    @unittest.skipIf(not HAVE_THREADS, 'need threads')
     def check_dump_traceback_threads(self, filename):
         """
         Call explicitly dump_traceback(all_threads=True) and check the output.
diff --git a/Lib/test/test_fork1.py b/Lib/test/test_fork1.py
index da46fe5..9ca9724 100644
--- a/Lib/test/test_fork1.py
+++ b/Lib/test/test_fork1.py
@@ -5,6 +5,7 @@ import _imp as imp
 import os
 import signal
 import sys
+import threading
 import time
 import unittest
 
@@ -12,7 +13,6 @@ from test.fork_wait import ForkWait
 from test.support import (reap_children, get_attribute,
                           import_module, verbose)
 
-threading = import_module('threading')
 
 # Skip test if fork does not exist.
 get_attribute(os, 'fork')
diff --git a/Lib/test/test_ftplib.py b/Lib/test/test_ftplib.py
index 24ea382..151e091 100644
--- a/Lib/test/test_ftplib.py
+++ b/Lib/test/test_ftplib.py
@@ -10,6 +10,7 @@ import socket
 import io
 import errno
 import os
+import threading
 import time
 try:
     import ssl
@@ -19,7 +20,6 @@ except ImportError:
 from unittest import TestCase, skipUnless
 from test import support
 from test.support import HOST, HOSTv6
-threading = support.import_module('threading')
 
 TIMEOUT = 3
 # the dummy data returned by server over the data channel when
diff --git a/Lib/test/test_functools.py b/Lib/test/test_functools.py
index 3acfb92..f7a1166 100644
--- a/Lib/test/test_functools.py
+++ b/Lib/test/test_functools.py
@@ -8,15 +8,12 @@ import pickle
 from random import choice
 import sys
 from test import support
+import threading
 import time
 import unittest
 import unittest.mock
 from weakref import proxy
 import contextlib
-try:
-    import threading
-except ImportError:
-    threading = None
 
 import functools
 
@@ -1406,7 +1403,6 @@ class TestLRU:
         for attr in self.module.WRAPPER_ASSIGNMENTS:
             self.assertEqual(getattr(g, attr), getattr(f, attr))
 
-    @unittest.skipUnless(threading, 'This test requires threading.')
     def test_lru_cache_threaded(self):
         n, m = 5, 11
         def orig(x, y):
@@ -1455,7 +1451,6 @@ class TestLRU:
         finally:
             sys.setswitchinterval(orig_si)
 
-    @unittest.skipUnless(threading, 'This test requires threading.')
     def test_lru_cache_threaded2(self):
         # Simultaneous call with the same arguments
         n, m = 5, 7
@@ -1483,7 +1478,6 @@ class TestLRU:
                 pause.reset()
                 self.assertEqual(f.cache_info(), (0, (i+1)*n, m*n, i+1))
 
-    @unittest.skipUnless(threading, 'This test requires threading.')
     def test_lru_cache_threaded3(self):
         @self.module.lru_cache(maxsize=2)
         def f(x):
diff --git a/Lib/test/test_gc.py b/Lib/test/test_gc.py
index e727499..914efec 100644
--- a/Lib/test/test_gc.py
+++ b/Lib/test/test_gc.py
@@ -8,11 +8,7 @@ import sys
 import time
 import gc
 import weakref
-
-try:
-    import threading
-except ImportError:
-    threading = None
+import threading
 
 try:
     from _testcapi import with_tp_del
@@ -352,7 +348,6 @@ class GCTests(unittest.TestCase):
                 v = {1: v, 2: Ouch()}
         gc.disable()
 
-    @unittest.skipUnless(threading, "test meaningless on builds without threads")
     def test_trashcan_threads(self):
         # Issue #13992: trashcan mechanism should be thread-safe
         NESTING = 60
diff --git a/Lib/test/test_gdb.py b/Lib/test/test_gdb.py
index 46736f6..9e0eaea 100644
--- a/Lib/test/test_gdb.py
+++ b/Lib/test/test_gdb.py
@@ -12,12 +12,6 @@ import sysconfig
 import textwrap
 import unittest
 
-# Is this Python configured to support threads?
-try:
-    import _thread
-except ImportError:
-    _thread = None
-
 from test import support
 from test.support import run_unittest, findfile, python_is_optimized
 
@@ -755,8 +749,6 @@ Traceback \(most recent call first\):
     foo\(1, 2, 3\)
 ''')
 
-    @unittest.skipUnless(_thread,
-                         "Python was compiled without thread support")
     def test_threads(self):
         'Verify that "py-bt" indicates threads that are waiting for the GIL'
         cmd = '''
@@ -794,8 +786,6 @@ id(42)
     # Some older versions of gdb will fail with
     #  "Cannot find new threads: generic error"
     # unless we add LD_PRELOAD=PATH-TO-libpthread.so.1 as a workaround
-    @unittest.skipUnless(_thread,
-                         "Python was compiled without thread support")
     def test_gc(self):
         'Verify that "py-bt" indicates if a thread is garbage-collecting'
         cmd = ('from gc import collect\n'
@@ -822,8 +812,6 @@ id(42)
     # Some older versions of gdb will fail with
     #  "Cannot find new threads: generic error"
     # unless we add LD_PRELOAD=PATH-TO-libpthread.so.1 as a workaround
-    @unittest.skipUnless(_thread,
-                         "Python was compiled without thread support")
     def test_pycfunction(self):
         'Verify that "py-bt" displays invocations of PyCFunction instances'
         # Tested function must not be defined with METH_NOARGS or METH_O,
diff --git a/Lib/test/test_hashlib.py b/Lib/test/test_hashlib.py
index f748b46..5c8f090 100644
--- a/Lib/test/test_hashlib.py
+++ b/Lib/test/test_hashlib.py
@@ -12,10 +12,7 @@ import hashlib
 import itertools
 import os
 import sys
-try:
-    import threading
-except ImportError:
-    threading = None
+import threading
 import unittest
 import warnings
 from test import support
@@ -738,7 +735,6 @@ class HashLibTestCase(unittest.TestCase):
         m = hashlib.md5(b'x' * gil_minsize)
         self.assertEqual(m.hexdigest(), 'cfb767f225d58469c5de3632a8803958')
 
-    @unittest.skipUnless(threading, 'Threading required for this test.')
     @support.reap_threads
     def test_threaded_hashing(self):
         # Updating the same hash object from several threads at once
diff --git a/Lib/test/test_httpservers.py b/Lib/test/test_httpservers.py
index 8cddcdc..20e6f66 100644
--- a/Lib/test/test_httpservers.py
+++ b/Lib/test/test_httpservers.py
@@ -22,12 +22,13 @@ import urllib.parse
 import tempfile
 import time
 import datetime
+import threading
 from unittest import mock
 from io import BytesIO
 
 import unittest
 from test import support
-threading = support.import_module('threading')
+
 
 class NoLogRequestHandler:
     def log_message(self, *args):
diff --git a/Lib/test/test_idle.py b/Lib/test/test_idle.py
index da05da5..b7ef70d 100644
--- a/Lib/test/test_idle.py
+++ b/Lib/test/test_idle.py
@@ -3,7 +3,6 @@ from test.support import import_module
 
 # Skip test if _thread or _tkinter wasn't built, if idlelib is missing,
 # or if tcl/tk is not the 8.5+ needed for ttk widgets.
-import_module('threading')  # imported by PyShell, imports _thread
 tk = import_module('tkinter')  # imports _tkinter
 if tk.TkVersion < 8.5:
     raise unittest.SkipTest("IDLE requires tk 8.5 or later.")
diff --git a/Lib/test/test_imaplib.py b/Lib/test/test_imaplib.py
index 7c12438..132c586 100644
--- a/Lib/test/test_imaplib.py
+++ b/Lib/test/test_imaplib.py
@@ -1,8 +1,4 @@
 from test import support
-# If we end up with a significant number of tests that don't require
-# threading, this test module should be split.  Right now we skip
-# them all if we don't have threading.
-threading = support.import_module('threading')
 
 from contextlib import contextmanager
 import imaplib
@@ -10,6 +6,7 @@ import os.path
 import socketserver
 import time
 import calendar
+import threading
 
 from test.support import (reap_threads, verbose, transient_internet,
                           run_with_tz, run_with_locale, cpython_only)
diff --git a/Lib/test/test_imp.py b/Lib/test/test_imp.py
index 6f35f49..3bfcb09 100644
--- a/Lib/test/test_imp.py
+++ b/Lib/test/test_imp.py
@@ -1,7 +1,3 @@
-try:
-    import _thread
-except ImportError:
-    _thread = None
 import importlib
 import importlib.util
 import os
@@ -23,7 +19,6 @@ def requires_load_dynamic(meth):
                            'imp.load_dynamic() required')(meth)
 
 
-@unittest.skipIf(_thread is None, '_thread module is required')
 class LockTests(unittest.TestCase):
 
     """Very basic test of import lock functions."""
diff --git a/Lib/test/test_importlib/test_locks.py b/Lib/test/test_importlib/test_locks.py
index dbce9c2..d86172a 100644
--- a/Lib/test/test_importlib/test_locks.py
+++ b/Lib/test/test_importlib/test_locks.py
@@ -3,134 +3,112 @@ from . import util as test_util
 init = test_util.import_importlib('importlib')
 
 import sys
+import threading
 import unittest
 import weakref
 
 from test import support
-
-try:
-    import threading
-except ImportError:
-    threading = None
-else:
-    from test import lock_tests
-
-if threading is not None:
-    class ModuleLockAsRLockTests:
-        locktype = classmethod(lambda cls: cls.LockType("some_lock"))
-
-        # _is_owned() unsupported
-        test__is_owned = None
-        # acquire(blocking=False) unsupported
-        test_try_acquire = None
-        test_try_acquire_contended = None
-        # `with` unsupported
-        test_with = None
-        # acquire(timeout=...) unsupported
-        test_timeout = None
-        # _release_save() unsupported
-        test_release_save_unacquired = None
-        # lock status in repr unsupported
-        test_repr = None
-        test_locked_repr = None
-
-    LOCK_TYPES = {kind: splitinit._bootstrap._ModuleLock
-                  for kind, splitinit in init.items()}
-
-    (Frozen_ModuleLockAsRLockTests,
-     Source_ModuleLockAsRLockTests
-     ) = test_util.test_both(ModuleLockAsRLockTests, lock_tests.RLockTests,
-                             LockType=LOCK_TYPES)
-else:
-    LOCK_TYPES = {}
-
-    class Frozen_ModuleLockAsRLockTests(unittest.TestCase):
-        pass
-
-    class Source_ModuleLockAsRLockTests(unittest.TestCase):
-        pass
-
-
-if threading is not None:
-    class DeadlockAvoidanceTests:
-
-        def setUp(self):
+from test import lock_tests
+
+
+class ModuleLockAsRLockTests:
+    locktype = classmethod(lambda cls: cls.LockType("some_lock"))
+
+    # _is_owned() unsupported
+    test__is_owned = None
+    # acquire(blocking=False) unsupported
+    test_try_acquire = None
+    test_try_acquire_contended = None
+    # `with` unsupported
+    test_with = None
+    # acquire(timeout=...) unsupported
+    test_timeout = None
+    # _release_save() unsupported
+    test_release_save_unacquired = None
+    # lock status in repr unsupported
+    test_repr = None
+    test_locked_repr = None
+
+LOCK_TYPES = {kind: splitinit._bootstrap._ModuleLock
+              for kind, splitinit in init.items()}
+
+(Frozen_ModuleLockAsRLockTests,
+ Source_ModuleLockAsRLockTests
+ ) = test_util.test_both(ModuleLockAsRLockTests, lock_tests.RLockTests,
+                         LockType=LOCK_TYPES)
+
+
+class DeadlockAvoidanceTests:
+
+    def setUp(self):
+        try:
+            self.old_switchinterval = sys.getswitchinterval()
+            support.setswitchinterval(0.000001)
+        except AttributeError:
+            self.old_switchinterval = None
+
+    def tearDown(self):
+        if self.old_switchinterval is not None:
+            sys.setswitchinterval(self.old_switchinterval)
+
+    def run_deadlock_avoidance_test(self, create_deadlock):
+        NLOCKS = 10
+        locks = [self.LockType(str(i)) for i in range(NLOCKS)]
+        pairs = [(locks[i], locks[(i+1)%NLOCKS]) for i in range(NLOCKS)]
+        if create_deadlock:
+            NTHREADS = NLOCKS
+        else:
+            NTHREADS = NLOCKS - 1
+        barrier = threading.Barrier(NTHREADS)
+        results = []
+
+        def _acquire(lock):
+            """Try to acquire the lock. Return True on success,
+            False on deadlock."""
             try:
-                self.old_switchinterval = sys.getswitchinterval()
-                support.setswitchinterval(0.000001)
-            except AttributeError:
-                self.old_switchinterval = None
-
-        def tearDown(self):
-            if self.old_switchinterval is not None:
-                sys.setswitchinterval(self.old_switchinterval)
-
-        def run_deadlock_avoidance_test(self, create_deadlock):
-            NLOCKS = 10
-            locks = [self.LockType(str(i)) for i in range(NLOCKS)]
-            pairs = [(locks[i], locks[(i+1)%NLOCKS]) for i in range(NLOCKS)]
-            if create_deadlock:
-                NTHREADS = NLOCKS
+                lock.acquire()
+            except self.DeadlockError:
+                return False
             else:
-                NTHREADS = NLOCKS - 1
-            barrier = threading.Barrier(NTHREADS)
-            results = []
-
-            def _acquire(lock):
-                """Try to acquire the lock. Return True on success,
-                False on deadlock."""
-                try:
-                    lock.acquire()
-                except self.DeadlockError:
-                    return False
-                else:
-                    return True
-
-            def f():
-                a, b = pairs.pop()
-                ra = _acquire(a)
-                barrier.wait()
-                rb = _acquire(b)
-                results.append((ra, rb))
-                if rb:
-                    b.release()
-                if ra:
-                    a.release()
-            lock_tests.Bunch(f, NTHREADS).wait_for_finished()
-            self.assertEqual(len(results), NTHREADS)
-            return results
-
-        def test_deadlock(self):
-            results = self.run_deadlock_avoidance_test(True)
-            # At least one of the threads detected a potential deadlock on its
-            # second acquire() call.  It may be several of them, because the
-            # deadlock avoidance mechanism is conservative.
-            nb_deadlocks = results.count((True, False))
-            self.assertGreaterEqual(nb_deadlocks, 1)
-            self.assertEqual(results.count((True, True)), len(results) - nb_deadlocks)
-
-        def test_no_deadlock(self):
-            results = self.run_deadlock_avoidance_test(False)
-            self.assertEqual(results.count((True, False)), 0)
-            self.assertEqual(results.count((True, True)), len(results))
-
-
-    DEADLOCK_ERRORS = {kind: splitinit._bootstrap._DeadlockError
-                       for kind, splitinit in init.items()}
-
-    (Frozen_DeadlockAvoidanceTests,
-     Source_DeadlockAvoidanceTests
-     ) = test_util.test_both(DeadlockAvoidanceTests,
-                             LockType=LOCK_TYPES,
-                             DeadlockError=DEADLOCK_ERRORS)
-else:
-    DEADLOCK_ERRORS = {}
-
-    class Frozen_DeadlockAvoidanceTests(unittest.TestCase):
-        pass
-
-    class Source_DeadlockAvoidanceTests(unittest.TestCase):
-        pass
+                return True
+
+        def f():
+            a, b = pairs.pop()
+            ra = _acquire(a)
+            barrier.wait()
+            rb = _acquire(b)
+            results.append((ra, rb))
+            if rb:
+                b.release()
+            if ra:
+                a.release()
+        lock_tests.Bunch(f, NTHREADS).wait_for_finished()
+        self.assertEqual(len(results), NTHREADS)
+        return results
+
+    def test_deadlock(self):
+        results = self.run_deadlock_avoidance_test(True)
+        # At least one of the threads detected a potential deadlock on its
+        # second acquire() call.  It may be several of them, because the
+        # deadlock avoidance mechanism is conservative.
+        nb_deadlocks = results.count((True, False))
+        self.assertGreaterEqual(nb_deadlocks, 1)
+        self.assertEqual(results.count((True, True)), len(results) - nb_deadlocks)
+
+    def test_no_deadlock(self):
+        results = self.run_deadlock_avoidance_test(False)
+        self.assertEqual(results.count((True, False)), 0)
+        self.assertEqual(results.count((True, True)), len(results))
+
+
+DEADLOCK_ERRORS = {kind: splitinit._bootstrap._DeadlockError
+                   for kind, splitinit in init.items()}
+
+(Frozen_DeadlockAvoidanceTests,
+ Source_DeadlockAvoidanceTests
+ ) = test_util.test_both(DeadlockAvoidanceTests,
+                         LockType=LOCK_TYPES,
+                         DeadlockError=DEADLOCK_ERRORS)
 
 
 class LifetimeTests:
diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py
index 48270c8..d4685dd 100644
--- a/Lib/test/test_io.py
+++ b/Lib/test/test_io.py
@@ -28,6 +28,7 @@ import pickle
 import random
 import signal
 import sys
+import threading
 import time
 import unittest
 import warnings
@@ -40,10 +41,6 @@ from test.support.script_helper import assert_python_ok, run_python_until_end
 import codecs
 import io  # C implementation of io
 import _pyio as pyio # Python implementation of io
-try:
-    import threading
-except ImportError:
-    threading = None
 
 try:
     import ctypes
@@ -443,8 +440,6 @@ class IOTest(unittest.TestCase):
             (self.BytesIO, "rws"), (self.StringIO, "rws"),
         )
         for [test, abilities] in tests:
-            if test is pipe_writer and not threading:
-                continue  # Skip subtest that uses a background thread
             with self.subTest(test), test() as obj:
                 readable = "r" in abilities
                 self.assertEqual(obj.readable(), readable)
@@ -1337,7 +1332,6 @@ class BufferedReaderTest(unittest.TestCase, CommonBufferedTests):
 
         self.assertEqual(b"abcdefg", bufio.read())
 
-    @unittest.skipUnless(threading, 'Threading required for this test.')
     @support.requires_resource('cpu')
     def test_threads(self):
         try:
@@ -1664,7 +1658,6 @@ class BufferedWriterTest(unittest.TestCase, CommonBufferedTests):
         with self.open(support.TESTFN, "rb", buffering=0) as f:
             self.assertEqual(f.read(), b"abc")
 
-    @unittest.skipUnless(threading, 'Threading required for this test.')
     @support.requires_resource('cpu')
     def test_threads(self):
         try:
@@ -3053,7 +3046,6 @@ class TextIOWrapperTest(unittest.TestCase):
             self.assertEqual(f.errors, "replace")
 
     @support.no_tracing
-    @unittest.skipUnless(threading, 'Threading required for this test.')
     def test_threads_write(self):
         # Issue6750: concurrent writes could duplicate data
         event = threading.Event()
@@ -3804,7 +3796,6 @@ class CMiscIOTest(MiscIOTest):
         b = bytearray(2)
         self.assertRaises(ValueError, bufio.readinto, b)
 
-    @unittest.skipUnless(threading, 'Threading required for this test.')
     def check_daemon_threads_shutdown_deadlock(self, stream_name):
         # Issue #23309: deadlocks at shutdown should be avoided when a
         # daemon thread and the main thread both write to a file.
@@ -3868,7 +3859,6 @@ class SignalsTest(unittest.TestCase):
     def alarm_interrupt(self, sig, frame):
         1/0
 
-    @unittest.skipUnless(threading, 'Threading required for this test.')
     def check_interrupted_write(self, item, bytes, **fdopen_kwargs):
         """Check that a partial write, when it gets interrupted, properly
         invokes the signal handler, and bubbles up the exception raised
@@ -3990,7 +3980,6 @@ class SignalsTest(unittest.TestCase):
         self.check_interrupted_read_retry(lambda x: x,
                                           mode="r")
 
-    @unittest.skipUnless(threading, 'Threading required for this test.')
     def check_interrupted_write_retry(self, item, **fdopen_kwargs):
         """Check that a buffered write, when it gets interrupted (either
         returning a partial result or EINTR), properly invokes the signal
diff --git a/Lib/test/test_logging.py b/Lib/test/test_logging.py
index f4aef9f..9c3816a 100644
--- a/Lib/test/test_logging.py
+++ b/Lib/test/test_logging.py
@@ -42,22 +42,19 @@ import tempfile
 from test.support.script_helper import assert_python_ok
 from test import support
 import textwrap
+import threading
 import time
 import unittest
 import warnings
 import weakref
-try:
-    import threading
-    # The following imports are needed only for tests which
-    # require threading
-    import asyncore
-    from http.server import HTTPServer, BaseHTTPRequestHandler
-    import smtpd
-    from urllib.parse import urlparse, parse_qs
-    from socketserver import (ThreadingUDPServer, DatagramRequestHandler,
-                              ThreadingTCPServer, StreamRequestHandler)
-except ImportError:
-    threading = None
+
+import asyncore
+from http.server import HTTPServer, BaseHTTPRequestHandler
+import smtpd
+from urllib.parse import urlparse, parse_qs
+from socketserver import (ThreadingUDPServer, DatagramRequestHandler,
+                          ThreadingTCPServer, StreamRequestHandler)
+
 try:
     import win32evtlog, win32evtlogutil, pywintypes
 except ImportError:
@@ -625,7 +622,6 @@ class HandlerTest(BaseTest):
             os.unlink(fn)
 
     @unittest.skipIf(os.name == 'nt', 'WatchedFileHandler not appropriate for Windows.')
-    @unittest.skipUnless(threading, 'Threading required for this test.')
     def test_race(self):
         # Issue #14632 refers.
         def remove_loop(fname, tries):
@@ -719,276 +715,274 @@ class StreamHandlerTest(BaseTest):
 # -- The following section could be moved into a server_helper.py module
 # -- if it proves to be of wider utility than just test_logging
 
-if threading:
-    class TestSMTPServer(smtpd.SMTPServer):
+class TestSMTPServer(smtpd.SMTPServer):
+    """
+    This class implements a test SMTP server.
+
+    :param addr: A (host, port) tuple which the server listens on.
+                 You can specify a port value of zero: the server's
+                 *port* attribute will hold the actual port number
+                 used, which can be used in client connections.
+    :param handler: A callable which will be called to process
+                    incoming messages. The handler will be passed
+                    the client address tuple, who the message is from,
+                    a list of recipients and the message data.
+    :param poll_interval: The interval, in seconds, used in the underlying
+                          :func:`select` or :func:`poll` call by
+                          :func:`asyncore.loop`.
+    :param sockmap: A dictionary which will be used to hold
+                    :class:`asyncore.dispatcher` instances used by
+                    :func:`asyncore.loop`. This avoids changing the
+                    :mod:`asyncore` module's global state.
+    """
+
+    def __init__(self, addr, handler, poll_interval, sockmap):
+        smtpd.SMTPServer.__init__(self, addr, None, map=sockmap,
+                                  decode_data=True)
+        self.port = self.socket.getsockname()[1]
+        self._handler = handler
+        self._thread = None
+        self.poll_interval = poll_interval
+
+    def process_message(self, peer, mailfrom, rcpttos, data):
+        """
+        Delegates to the handler passed in to the server's constructor.
+
+        Typically, this will be a test case method.
+        :param peer: The client (host, port) tuple.
+        :param mailfrom: The address of the sender.
+        :param rcpttos: The addresses of the recipients.
+        :param data: The message.
         """
-        This class implements a test SMTP server.
-
-        :param addr: A (host, port) tuple which the server listens on.
-                     You can specify a port value of zero: the server's
-                     *port* attribute will hold the actual port number
-                     used, which can be used in client connections.
-        :param handler: A callable which will be called to process
-                        incoming messages. The handler will be passed
-                        the client address tuple, who the message is from,
-                        a list of recipients and the message data.
+        self._handler(peer, mailfrom, rcpttos, data)
+
+    def start(self):
+        """
+        Start the server running on a separate daemon thread.
+        """
+        self._thread = t = threading.Thread(target=self.serve_forever,
+                                            args=(self.poll_interval,))
+        t.setDaemon(True)
+        t.start()
+
+    def serve_forever(self, poll_interval):
+        """
+        Run the :mod:`asyncore` loop until normal termination
+        conditions arise.
         :param poll_interval: The interval, in seconds, used in the underlying
                               :func:`select` or :func:`poll` call by
                               :func:`asyncore.loop`.
-        :param sockmap: A dictionary which will be used to hold
-                        :class:`asyncore.dispatcher` instances used by
-                        :func:`asyncore.loop`. This avoids changing the
-                        :mod:`asyncore` module's global state.
         """
+        try:
+            asyncore.loop(poll_interval, map=self._map)
+        except OSError:
+            # On FreeBSD 8, closing the server repeatably
+            # raises this error. We swallow it if the
+            # server has been closed.
+            if self.connected or self.accepting:
+                raise
 
-        def __init__(self, addr, handler, poll_interval, sockmap):
-            smtpd.SMTPServer.__init__(self, addr, None, map=sockmap,
-                                      decode_data=True)
-            self.port = self.socket.getsockname()[1]
-            self._handler = handler
-            self._thread = None
-            self.poll_interval = poll_interval
+    def stop(self, timeout=None):
+        """
+        Stop the thread by closing the server instance.
+        Wait for the server thread to terminate.
 
-        def process_message(self, peer, mailfrom, rcpttos, data):
-            """
-            Delegates to the handler passed in to the server's constructor.
+        :param timeout: How long to wait for the server thread
+                        to terminate.
+        """
+        self.close()
+        self._thread.join(timeout)
+        asyncore.close_all(map=self._map, ignore_all=True)
 
-            Typically, this will be a test case method.
-            :param peer: The client (host, port) tuple.
-            :param mailfrom: The address of the sender.
-            :param rcpttos: The addresses of the recipients.
-            :param data: The message.
-            """
-            self._handler(peer, mailfrom, rcpttos, data)
+        alive = self._thread.is_alive()
+        self._thread = None
+        if alive:
+            self.fail("join() timed out")
 
-        def start(self):
-            """
-            Start the server running on a separate daemon thread.
-            """
-            self._thread = t = threading.Thread(target=self.serve_forever,
-                                                args=(self.poll_interval,))
-            t.setDaemon(True)
-            t.start()
+class ControlMixin(object):
+    """
+    This mixin is used to start a server on a separate thread, and
+    shut it down programmatically. Request handling is simplified - instead
+    of needing to derive a suitable RequestHandler subclass, you just
+    provide a callable which will be passed each received request to be
+    processed.
+
+    :param handler: A handler callable which will be called with a
+                    single parameter - the request - in order to
+                    process the request. This handler is called on the
+                    server thread, effectively meaning that requests are
+                    processed serially. While not quite Web scale ;-),
+                    this should be fine for testing applications.
+    :param poll_interval: The polling interval in seconds.
+    """
+    def __init__(self, handler, poll_interval):
+        self._thread = None
+        self.poll_interval = poll_interval
+        self._handler = handler
+        self.ready = threading.Event()
 
-        def serve_forever(self, poll_interval):
-            """
-            Run the :mod:`asyncore` loop until normal termination
-            conditions arise.
-            :param poll_interval: The interval, in seconds, used in the underlying
-                                  :func:`select` or :func:`poll` call by
-                                  :func:`asyncore.loop`.
-            """
-            try:
-                asyncore.loop(poll_interval, map=self._map)
-            except OSError:
-                # On FreeBSD 8, closing the server repeatably
-                # raises this error. We swallow it if the
-                # server has been closed.
-                if self.connected or self.accepting:
-                    raise
-
-        def stop(self, timeout=None):
-            """
-            Stop the thread by closing the server instance.
-            Wait for the server thread to terminate.
+    def start(self):
+        """
+        Create a daemon thread to run the server, and start it.
+        """
+        self._thread = t = threading.Thread(target=self.serve_forever,
+                                            args=(self.poll_interval,))
+        t.setDaemon(True)
+        t.start()
 
-            :param timeout: How long to wait for the server thread
-                            to terminate.
-            """
-            self.close()
-            self._thread.join(timeout)
-            asyncore.close_all(map=self._map, ignore_all=True)
+    def serve_forever(self, poll_interval):
+        """
+        Run the server. Set the ready flag before entering the
+        service loop.
+        """
+        self.ready.set()
+        super(ControlMixin, self).serve_forever(poll_interval)
 
+    def stop(self, timeout=None):
+        """
+        Tell the server thread to stop, and wait for it to do so.
+
+        :param timeout: How long to wait for the server thread
+                        to terminate.
+        """
+        self.shutdown()
+        if self._thread is not None:
+            self._thread.join(timeout)
             alive = self._thread.is_alive()
             self._thread = None
             if alive:
                 self.fail("join() timed out")
+        self.server_close()
+        self.ready.clear()
 
-    class ControlMixin(object):
-        """
-        This mixin is used to start a server on a separate thread, and
-        shut it down programmatically. Request handling is simplified - instead
-        of needing to derive a suitable RequestHandler subclass, you just
-        provide a callable which will be passed each received request to be
-        processed.
-
-        :param handler: A handler callable which will be called with a
-                        single parameter - the request - in order to
-                        process the request. This handler is called on the
-                        server thread, effectively meaning that requests are
-                        processed serially. While not quite Web scale ;-),
-                        this should be fine for testing applications.
-        :param poll_interval: The polling interval in seconds.
-        """
-        def __init__(self, handler, poll_interval):
-            self._thread = None
-            self.poll_interval = poll_interval
-            self._handler = handler
-            self.ready = threading.Event()
+class TestHTTPServer(ControlMixin, HTTPServer):
+    """
+    An HTTP server which is controllable using :class:`ControlMixin`.
+
+    :param addr: A tuple with the IP address and port to listen on.
+    :param handler: A handler callable which will be called with a
+                    single parameter - the request - in order to
+                    process the request.
+    :param poll_interval: The polling interval in seconds.
+    :param log: Pass ``True`` to enable log messages.
+    """
+    def __init__(self, addr, handler, poll_interval=0.5,
+                 log=False, sslctx=None):
+        class DelegatingHTTPRequestHandler(BaseHTTPRequestHandler):
+            def __getattr__(self, name, default=None):
+                if name.startswith('do_'):
+                    return self.process_request
+                raise AttributeError(name)
+
+            def process_request(self):
+                self.server._handler(self)
+
+            def log_message(self, format, *args):
+                if log:
+                    super(DelegatingHTTPRequestHandler,
+                          self).log_message(format, *args)
+        HTTPServer.__init__(self, addr, DelegatingHTTPRequestHandler)
+        ControlMixin.__init__(self, handler, poll_interval)
+        self.sslctx = sslctx
+
+    def get_request(self):
+        try:
+            sock, addr = self.socket.accept()
+            if self.sslctx:
+                sock = self.sslctx.wrap_socket(sock, server_side=True)
+        except OSError as e:
+            # socket errors are silenced by the caller, print them here
+            sys.stderr.write("Got an error:\n%s\n" % e)
+            raise
+        return sock, addr
 
-        def start(self):
-            """
-            Create a daemon thread to run the server, and start it.
-            """
-            self._thread = t = threading.Thread(target=self.serve_forever,
-                                                args=(self.poll_interval,))
-            t.setDaemon(True)
-            t.start()
+class TestTCPServer(ControlMixin, ThreadingTCPServer):
+    """
+    A TCP server which is controllable using :class:`ControlMixin`.
+
+    :param addr: A tuple with the IP address and port to listen on.
+    :param handler: A handler callable which will be called with a single
+                    parameter - the request - in order to process the request.
+    :param poll_interval: The polling interval in seconds.
+    :bind_and_activate: If True (the default), binds the server and starts it
+                        listening. If False, you need to call
+                        :meth:`server_bind` and :meth:`server_activate` at
+                        some later time before calling :meth:`start`, so that
+                        the server will set up the socket and listen on it.
+    """
 
-        def serve_forever(self, poll_interval):
-            """
-            Run the server. Set the ready flag before entering the
-            service loop.
-            """
-            self.ready.set()
-            super(ControlMixin, self).serve_forever(poll_interval)
+    allow_reuse_address = True
 
-        def stop(self, timeout=None):
-            """
-            Tell the server thread to stop, and wait for it to do so.
+    def __init__(self, addr, handler, poll_interval=0.5,
+                 bind_and_activate=True):
+        class DelegatingTCPRequestHandler(StreamRequestHandler):
 
-            :param timeout: How long to wait for the server thread
-                            to terminate.
-            """
-            self.shutdown()
-            if self._thread is not None:
-                self._thread.join(timeout)
-                alive = self._thread.is_alive()
-                self._thread = None
-                if alive:
-                    self.fail("join() timed out")
-            self.server_close()
-            self.ready.clear()
-
-    class TestHTTPServer(ControlMixin, HTTPServer):
-        """
-        An HTTP server which is controllable using :class:`ControlMixin`.
-
-        :param addr: A tuple with the IP address and port to listen on.
-        :param handler: A handler callable which will be called with a
-                        single parameter - the request - in order to
-                        process the request.
-        :param poll_interval: The polling interval in seconds.
-        :param log: Pass ``True`` to enable log messages.
-        """
-        def __init__(self, addr, handler, poll_interval=0.5,
-                     log=False, sslctx=None):
-            class DelegatingHTTPRequestHandler(BaseHTTPRequestHandler):
-                def __getattr__(self, name, default=None):
-                    if name.startswith('do_'):
-                        return self.process_request
-                    raise AttributeError(name)
-
-                def process_request(self):
-                    self.server._handler(self)
-
-                def log_message(self, format, *args):
-                    if log:
-                        super(DelegatingHTTPRequestHandler,
-                              self).log_message(format, *args)
-            HTTPServer.__init__(self, addr, DelegatingHTTPRequestHandler)
-            ControlMixin.__init__(self, handler, poll_interval)
-            self.sslctx = sslctx
-
-        def get_request(self):
-            try:
-                sock, addr = self.socket.accept()
-                if self.sslctx:
-                    sock = self.sslctx.wrap_socket(sock, server_side=True)
-            except OSError as e:
-                # socket errors are silenced by the caller, print them here
-                sys.stderr.write("Got an error:\n%s\n" % e)
-                raise
-            return sock, addr
+            def handle(self):
+                self.server._handler(self)
+        ThreadingTCPServer.__init__(self, addr, DelegatingTCPRequestHandler,
+                                    bind_and_activate)
+        ControlMixin.__init__(self, handler, poll_interval)
 
-    class TestTCPServer(ControlMixin, ThreadingTCPServer):
-        """
-        A TCP server which is controllable using :class:`ControlMixin`.
-
-        :param addr: A tuple with the IP address and port to listen on.
-        :param handler: A handler callable which will be called with a single
-                        parameter - the request - in order to process the request.
-        :param poll_interval: The polling interval in seconds.
-        :bind_and_activate: If True (the default), binds the server and starts it
-                            listening. If False, you need to call
-                            :meth:`server_bind` and :meth:`server_activate` at
-                            some later time before calling :meth:`start`, so that
-                            the server will set up the socket and listen on it.
-        """
+    def server_bind(self):
+        super(TestTCPServer, self).server_bind()
+        self.port = self.socket.getsockname()[1]
 
-        allow_reuse_address = True
+class TestUDPServer(ControlMixin, ThreadingUDPServer):
+    """
+    A UDP server which is controllable using :class:`ControlMixin`.
+
+    :param addr: A tuple with the IP address and port to listen on.
+    :param handler: A handler callable which will be called with a
+                    single parameter - the request - in order to
+                    process the request.
+    :param poll_interval: The polling interval for shutdown requests,
+                          in seconds.
+    :bind_and_activate: If True (the default), binds the server and
+                        starts it listening. If False, you need to
+                        call :meth:`server_bind` and
+                        :meth:`server_activate` at some later time
+                        before calling :meth:`start`, so that the server will
+                        set up the socket and listen on it.
+    """
+    def __init__(self, addr, handler, poll_interval=0.5,
+                 bind_and_activate=True):
+        class DelegatingUDPRequestHandler(DatagramRequestHandler):
 
-        def __init__(self, addr, handler, poll_interval=0.5,
-                     bind_and_activate=True):
-            class DelegatingTCPRequestHandler(StreamRequestHandler):
+            def handle(self):
+                self.server._handler(self)
 
-                def handle(self):
-                    self.server._handler(self)
-            ThreadingTCPServer.__init__(self, addr, DelegatingTCPRequestHandler,
-                                        bind_and_activate)
-            ControlMixin.__init__(self, handler, poll_interval)
+            def finish(self):
+                data = self.wfile.getvalue()
+                if data:
+                    try:
+                        super(DelegatingUDPRequestHandler, self).finish()
+                    except OSError:
+                        if not self.server._closed:
+                            raise
 
-        def server_bind(self):
-            super(TestTCPServer, self).server_bind()
-            self.port = self.socket.getsockname()[1]
+        ThreadingUDPServer.__init__(self, addr,
+                                    DelegatingUDPRequestHandler,
+                                    bind_and_activate)
+        ControlMixin.__init__(self, handler, poll_interval)
+        self._closed = False
 
-    class TestUDPServer(ControlMixin, ThreadingUDPServer):
-        """
-        A UDP server which is controllable using :class:`ControlMixin`.
-
-        :param addr: A tuple with the IP address and port to listen on.
-        :param handler: A handler callable which will be called with a
-                        single parameter - the request - in order to
-                        process the request.
-        :param poll_interval: The polling interval for shutdown requests,
-                              in seconds.
-        :bind_and_activate: If True (the default), binds the server and
-                            starts it listening. If False, you need to
-                            call :meth:`server_bind` and
-                            :meth:`server_activate` at some later time
-                            before calling :meth:`start`, so that the server will
-                            set up the socket and listen on it.
-        """
-        def __init__(self, addr, handler, poll_interval=0.5,
-                     bind_and_activate=True):
-            class DelegatingUDPRequestHandler(DatagramRequestHandler):
-
-                def handle(self):
-                    self.server._handler(self)
-
-                def finish(self):
-                    data = self.wfile.getvalue()
-                    if data:
-                        try:
-                            super(DelegatingUDPRequestHandler, self).finish()
-                        except OSError:
-                            if not self.server._closed:
-                                raise
-
-            ThreadingUDPServer.__init__(self, addr,
-                                        DelegatingUDPRequestHandler,
-                                        bind_and_activate)
-            ControlMixin.__init__(self, handler, poll_interval)
-            self._closed = False
-
-        def server_bind(self):
-            super(TestUDPServer, self).server_bind()
-            self.port = self.socket.getsockname()[1]
-
-        def server_close(self):
-            super(TestUDPServer, self).server_close()
-            self._closed = True
+    def server_bind(self):
+        super(TestUDPServer, self).server_bind()
+        self.port = self.socket.getsockname()[1]
 
-    if hasattr(socket, "AF_UNIX"):
-        class TestUnixStreamServer(TestTCPServer):
-            address_family = socket.AF_UNIX
+    def server_close(self):
+        super(TestUDPServer, self).server_close()
+        self._closed = True
 
-        class TestUnixDatagramServer(TestUDPServer):
-            address_family = socket.AF_UNIX
+if hasattr(socket, "AF_UNIX"):
+    class TestUnixStreamServer(TestTCPServer):
+        address_family = socket.AF_UNIX
+
+    class TestUnixDatagramServer(TestUDPServer):
+        address_family = socket.AF_UNIX
 
 # - end of server_helper section
 
-@unittest.skipUnless(threading, 'Threading required for this test.')
 class SMTPHandlerTest(BaseTest):
     TIMEOUT = 8.0
 
@@ -1472,14 +1466,12 @@ class ConfigFileTest(BaseTest):
 
 
 @unittest.skipIf(True, "FIXME: bpo-30830")
-@unittest.skipUnless(threading, 'Threading required for this test.')
 class SocketHandlerTest(BaseTest):
 
     """Test for SocketHandler objects."""
 
-    if threading:
-        server_class = TestTCPServer
-        address = ('localhost', 0)
+    server_class = TestTCPServer
+    address = ('localhost', 0)
 
     def setUp(self):
         """Set up a TCP server to receive log messages, and a SocketHandler
@@ -1573,12 +1565,11 @@ def _get_temp_domain_socket():
 
 @unittest.skipIf(True, "FIXME: bpo-30830")
 @unittest.skipUnless(hasattr(socket, "AF_UNIX"), "Unix sockets required")
-@unittest.skipUnless(threading, 'Threading required for this test.')
 class UnixSocketHandlerTest(SocketHandlerTest):
 
     """Test for SocketHandler with unix sockets."""
 
-    if threading and hasattr(socket, "AF_UNIX"):
+    if hasattr(socket, "AF_UNIX"):
         server_class = TestUnixStreamServer
 
     def setUp(self):
@@ -1591,14 +1582,12 @@ class UnixSocketHandlerTest(SocketHandlerTest):
         support.unlink(self.address)
 
 @unittest.skipIf(True, "FIXME: bpo-30830")
-@unittest.skipUnless(threading, 'Threading required for this test.')
 class DatagramHandlerTest(BaseTest):
 
     """Test for DatagramHandler."""
 
-    if threading:
-        server_class = TestUDPServer
-        address = ('localhost', 0)
+    server_class = TestUDPServer
+    address = ('localhost', 0)
 
     def setUp(self):
         """Set up a UDP server to receive log messages, and a DatagramHandler
@@ -1659,12 +1648,11 @@ class DatagramHandlerTest(BaseTest):
 
 @unittest.skipIf(True, "FIXME: bpo-30830")
 @unittest.skipUnless(hasattr(socket, "AF_UNIX"), "Unix sockets required")
-@unittest.skipUnless(threading, 'Threading required for this test.')
 class UnixDatagramHandlerTest(DatagramHandlerTest):
 
     """Test for DatagramHandler using Unix sockets."""
 
-    if threading and hasattr(socket, "AF_UNIX"):
+    if hasattr(socket, "AF_UNIX"):
         server_class = TestUnixDatagramServer
 
     def setUp(self):
@@ -1676,14 +1664,12 @@ class UnixDatagramHandlerTest(DatagramHandlerTest):
         DatagramHandlerTest.tearDown(self)
         support.unlink(self.address)
 
-@unittest.skipUnless(threading, 'Threading required for this test.')
 class SysLogHandlerTest(BaseTest):
 
     """Test for SysLogHandler using UDP."""
 
-    if threading:
-        server_class = TestUDPServer
-        address = ('localhost', 0)
+    server_class = TestUDPServer
+    address = ('localhost', 0)
 
     def setUp(self):
         """Set up a UDP server to receive log messages, and a SysLogHandler
@@ -1747,12 +1733,11 @@ class SysLogHandlerTest(BaseTest):
 
 @unittest.skipIf(True, "FIXME: bpo-30830")
 @unittest.skipUnless(hasattr(socket, "AF_UNIX"), "Unix sockets required")
-@unittest.skipUnless(threading, 'Threading required for this test.')
 class UnixSysLogHandlerTest(SysLogHandlerTest):
 
     """Test for SysLogHandler with Unix sockets."""
 
-    if threading and hasattr(socket, "AF_UNIX"):
+    if hasattr(socket, "AF_UNIX"):
         server_class = TestUnixDatagramServer
 
     def setUp(self):
@@ -1767,7 +1752,6 @@ class UnixSysLogHandlerTest(SysLogHandlerTest):
 @unittest.skipIf(True, "FIXME: bpo-30830")
 @unittest.skipUnless(support.IPV6_ENABLED,
                      'IPv6 support required for this test.')
-@unittest.skipUnless(threading, 'Threading required for this test.')
 class IPv6SysLogHandlerTest(SysLogHandlerTest):
 
     """Test for SysLogHandler with IPv6 host."""
@@ -1783,7 +1767,6 @@ class IPv6SysLogHandlerTest(SysLogHandlerTest):
         self.server_class.address_family = socket.AF_INET
         super(IPv6SysLogHandlerTest, self).tearDown()
 
-@unittest.skipUnless(threading, 'Threading required for this test.')
 class HTTPHandlerTest(BaseTest):
     """Test for HTTPHandler."""
 
@@ -2892,7 +2875,6 @@ class ConfigDictTest(BaseTest):
     # listen() uses ConfigSocketReceiver which is based
     # on socketserver.ThreadingTCPServer
     @unittest.skipIf(True, "FIXME: bpo-30830")
-    @unittest.skipUnless(threading, 'listen() needs threading to work')
     def setup_via_listener(self, text, verify=None):
         text = text.encode("utf-8")
         # Ask for a randomly assigned port (by using port 0)
@@ -2923,7 +2905,6 @@ class ConfigDictTest(BaseTest):
             if t.is_alive():
                 self.fail("join() timed out")
 
-    @unittest.skipUnless(threading, 'Threading required for this test.')
     def test_listen_config_10_ok(self):
         with support.captured_stdout() as output:
             self.setup_via_listener(json.dumps(self.config10))
@@ -2943,7 +2924,6 @@ class ConfigDictTest(BaseTest):
                 ('ERROR', '4'),
             ], stream=output)
 
-    @unittest.skipUnless(threading, 'Threading required for this test.')
     def test_listen_config_1_ok(self):
         with support.captured_stdout() as output:
             self.setup_via_listener(textwrap.dedent(ConfigFileTest.config1))
@@ -2958,7 +2938,6 @@ class ConfigDictTest(BaseTest):
             # Original logger output is empty.
             self.assert_log_lines([])
 
-    @unittest.skipUnless(threading, 'Threading required for this test.')
     def test_listen_verify(self):
 
         def verify_fail(stuff):
@@ -3713,9 +3692,8 @@ class LogRecordTest(BaseTest):
     def test_optional(self):
         r = logging.makeLogRecord({})
         NOT_NONE = self.assertIsNotNone
-        if threading:
-            NOT_NONE(r.thread)
-            NOT_NONE(r.threadName)
+        NOT_NONE(r.thread)
+        NOT_NONE(r.threadName)
         NOT_NONE(r.process)
         NOT_NONE(r.processName)
         log_threads = logging.logThreads
diff --git a/Lib/test/test_nntplib.py b/Lib/test/test_nntplib.py
index e2cd36a..bb780bf 100644
--- a/Lib/test/test_nntplib.py
+++ b/Lib/test/test_nntplib.py
@@ -6,6 +6,8 @@ import unittest
 import functools
 import contextlib
 import os.path
+import threading
+
 from test import support
 from nntplib import NNTP, GroupInfo
 import nntplib
@@ -14,10 +16,7 @@ try:
     import ssl
 except ImportError:
     ssl = None
-try:
-    import threading
-except ImportError:
-    threading = None
+
 
 TIMEOUT = 30
 certfile = os.path.join(os.path.dirname(__file__), 'keycert3.pem')
@@ -1520,7 +1519,7 @@ class MockSslTests(MockSocketTests):
     def nntp_class(*pos, **kw):
         return nntplib.NNTP_SSL(*pos, ssl_context=bypass_context, **kw)
 
-@unittest.skipUnless(threading, 'requires multithreading')
+
 class LocalServerTests(unittest.TestCase):
     def setUp(self):
         sock = socket.socket()
diff --git a/Lib/test/test_os.py b/Lib/test/test_os.py
index 234f701..c3c8238 100644
--- a/Lib/test/test_os.py
+++ b/Lib/test/test_os.py
@@ -22,15 +22,13 @@ import stat
 import subprocess
 import sys
 import sysconfig
+import threading
 import time
 import unittest
 import uuid
 import warnings
 from test import support
-try:
-    import threading
-except ImportError:
-    threading = None
+
 try:
     import resource
 except ImportError:
@@ -2516,92 +2514,90 @@ class ProgramPriorityTests(unittest.TestCase):
                     raise
 
 
-if threading is not None:
-    class SendfileTestServer(asyncore.dispatcher, threading.Thread):
-
-        class Handler(asynchat.async_chat):
+class SendfileTestServer(asyncore.dispatcher, threading.Thread):
 
-            def __init__(self, conn):
-                asynchat.async_chat.__init__(self, conn)
-                self.in_buffer = []
-                self.closed = False
-                self.push(b"220 ready\r\n")
+    class Handler(asynchat.async_chat):
 
-            def handle_read(self):
-                data = self.recv(4096)
-                self.in_buffer.append(data)
+        def __init__(self, conn):
+            asynchat.async_chat.__init__(self, conn)
+            self.in_buffer = []
+            self.closed = False
+            self.push(b"220 ready\r\n")
 
-            def get_data(self):
-                return b''.join(self.in_buffer)
+        def handle_read(self):
+            data = self.recv(4096)
+            self.in_buffer.append(data)
 
-            def handle_close(self):
-                self.close()
-                self.closed = True
+        def get_data(self):
+            return b''.join(self.in_buffer)
 
-            def handle_error(self):
-                raise
-
-        def __init__(self, address):
-            threading.Thread.__init__(self)
-            asyncore.dispatcher.__init__(self)
-            self.create_socket(socket.AF_INET, socket.SOCK_STREAM)
-            self.bind(address)
-            self.listen(5)
-            self.host, self.port = self.socket.getsockname()[:2]
-            self.handler_instance = None
-            self._active = False
-            self._active_lock = threading.Lock()
-
-        # --- public API
-
-        @property
-        def running(self):
-            return self._active
-
-        def start(self):
-            assert not self.running
-            self.__flag = threading.Event()
-            threading.Thread.start(self)
-            self.__flag.wait()
-
-        def stop(self):
-            assert self.running
-            self._active = False
-            self.join()
-
-        def wait(self):
-            # wait for handler connection to be closed, then stop the server
-            while not getattr(self.handler_instance, "closed", False):
-                time.sleep(0.001)
-            self.stop()
-
-        # --- internals
-
-        def run(self):
-            self._active = True
-            self.__flag.set()
-            while self._active and asyncore.socket_map:
-                self._active_lock.acquire()
-                asyncore.loop(timeout=0.001, count=1)
-                self._active_lock.release()
-            asyncore.close_all()
-
-        def handle_accept(self):
-            conn, addr = self.accept()
-            self.handler_instance = self.Handler(conn)
-
-        def handle_connect(self):
+        def handle_close(self):
             self.close()
-        handle_read = handle_connect
-
-        def writable(self):
-            return 0
+            self.closed = True
 
         def handle_error(self):
             raise
 
+    def __init__(self, address):
+        threading.Thread.__init__(self)
+        asyncore.dispatcher.__init__(self)
+        self.create_socket(socket.AF_INET, socket.SOCK_STREAM)
+        self.bind(address)
+        self.listen(5)
+        self.host, self.port = self.socket.getsockname()[:2]
+        self.handler_instance = None
+        self._active = False
+        self._active_lock = threading.Lock()
+
+    # --- public API
+
+    @property
+    def running(self):
+        return self._active
+
+    def start(self):
+        assert not self.running
+        self.__flag = threading.Event()
+        threading.Thread.start(self)
+        self.__flag.wait()
+
+    def stop(self):
+        assert self.running
+        self._active = False
+        self.join()
+
+    def wait(self):
+        # wait for handler connection to be closed, then stop the server
+        while not getattr(self.handler_instance, "closed", False):
+            time.sleep(0.001)
+        self.stop()
+
+    # --- internals
+
+    def run(self):
+        self._active = True
+        self.__flag.set()
+        while self._active and asyncore.socket_map:
+            self._active_lock.acquire()
+            asyncore.loop(timeout=0.001, count=1)
+            self._active_lock.release()
+        asyncore.close_all()
+
+    def handle_accept(self):
+        conn, addr = self.accept()
+        self.handler_instance = self.Handler(conn)
+
+    def handle_connect(self):
+        self.close()
+    handle_read = handle_connect
+
+    def writable(self):
+        return 0
+
+    def handle_error(self):
+        raise
+
 
-@unittest.skipUnless(threading is not None, "test needs threading module")
 @unittest.skipUnless(hasattr(os, 'sendfile'), "test needs os.sendfile()")
 class TestSendfile(unittest.TestCase):
 
diff --git a/Lib/test/test_pdb.py b/Lib/test/test_pdb.py
index 0ea2af5..755d265 100644
--- a/Lib/test/test_pdb.py
+++ b/Lib/test/test_pdb.py
@@ -1040,9 +1040,6 @@ class PdbTestCase(unittest.TestCase):
         # invoking "continue" on a non-main thread triggered an exception
         # inside signal.signal
 
-        # raises SkipTest if python was built without threads
-        support.import_module('threading')
-
         with open(support.TESTFN, 'wb') as f:
             f.write(textwrap.dedent("""
                 import threading
diff --git a/Lib/test/test_poll.py b/Lib/test/test_poll.py
index 6a2bf6e..16c2d2e 100644
--- a/Lib/test/test_poll.py
+++ b/Lib/test/test_poll.py
@@ -4,10 +4,7 @@ import os
 import subprocess
 import random
 import select
-try:
-    import threading
-except ImportError:
-    threading = None
+import threading
 import time
 import unittest
 from test.support import TESTFN, run_unittest, reap_threads, cpython_only
@@ -179,7 +176,6 @@ class PollTests(unittest.TestCase):
         self.assertRaises(OverflowError, pollster.poll, INT_MAX + 1)
         self.assertRaises(OverflowError, pollster.poll, UINT_MAX + 1)
 
-    @unittest.skipUnless(threading, 'Threading required for this test.')
     @reap_threads
     def test_threaded_poll(self):
         r, w = os.pipe()
diff --git a/Lib/test/test_poplib.py b/Lib/test/test_poplib.py
index e5b16dc..92febbf 100644
--- a/Lib/test/test_poplib.py
+++ b/Lib/test/test_poplib.py
@@ -9,10 +9,10 @@ import asynchat
 import socket
 import os
 import errno
+import threading
 
 from unittest import TestCase, skipUnless
 from test import support as test_support
-threading = test_support.import_module('threading')
 
 HOST = test_support.HOST
 PORT = 0
diff --git a/Lib/test/test_pydoc.py b/Lib/test/test_pydoc.py
index d68ab55..1ac08ed 100644
--- a/Lib/test/test_pydoc.py
+++ b/Lib/test/test_pydoc.py
@@ -20,6 +20,7 @@ import urllib.parse
 import xml.etree
 import xml.etree.ElementTree
 import textwrap
+import threading
 from io import StringIO
 from collections import namedtuple
 from test.support.script_helper import assert_python_ok
@@ -30,10 +31,6 @@ from test.support import (
 )
 from test import pydoc_mod
 
-try:
-    import threading
-except ImportError:
-    threading = None
 
 class nonascii:
     'Це не латиниця'
@@ -902,7 +899,6 @@ class TestDescriptions(unittest.TestCase):
             "stat(path, *, dir_fd=None, follow_symlinks=True)")
 
 
-@unittest.skipUnless(threading, 'Threading required for this test.')
 class PydocServerTest(unittest.TestCase):
     """Tests for pydoc._start_server"""
 
diff --git a/Lib/test/test_queue.py b/Lib/test/test_queue.py
index 4ccaa39..718ed67 100644
--- a/Lib/test/test_queue.py
+++ b/Lib/test/test_queue.py
@@ -1,10 +1,11 @@
 # Some simple queue module tests, plus some failure conditions
 # to ensure the Queue locks remain stable.
 import queue
+import threading
 import time
 import unittest
 from test import support
-threading = support.import_module('threading')
+
 
 QUEUE_SIZE = 5
 
diff --git a/Lib/test/test_regrtest.py b/Lib/test/test_regrtest.py
index b756839..8364767 100644
--- a/Lib/test/test_regrtest.py
+++ b/Lib/test/test_regrtest.py
@@ -15,6 +15,7 @@ import sys
 import sysconfig
 import tempfile
 import textwrap
+import threading
 import unittest
 from test import libregrtest
 from test import support
@@ -741,12 +742,7 @@ class ArgsTestCase(BaseTestCase):
         code = TEST_INTERRUPTED
         test = self.create_test("sigint", code=code)
 
-        try:
-            import threading
-            tests = (False, True)
-        except ImportError:
-            tests = (False,)
-        for multiprocessing in tests:
+        for multiprocessing in (False, True):
             if multiprocessing:
                 args = ("--slowest", "-j2", test)
             else:
diff --git a/Lib/test/test_robotparser.py b/Lib/test/test_robotparser.py
index 0f64ba8..5c1a571 100644
--- a/Lib/test/test_robotparser.py
+++ b/Lib/test/test_robotparser.py
@@ -1,14 +1,11 @@
 import io
 import os
+import threading
 import unittest
 import urllib.robotparser
 from collections import namedtuple
 from test import support
 from http.server import BaseHTTPRequestHandler, HTTPServer
-try:
-    import threading
-except ImportError:
-    threading = None
 
 
 class BaseRobotTest:
@@ -255,7 +252,6 @@ class RobotHandler(BaseHTTPRequestHandler):
         pass
 
 
-@unittest.skipUnless(threading, 'threading required for this test')
 class PasswordProtectedSiteTestCase(unittest.TestCase):
 
     def setUp(self):
diff --git a/Lib/test/test_sched.py b/Lib/test/test_sched.py
index ebf8856..794c637 100644
--- a/Lib/test/test_sched.py
+++ b/Lib/test/test_sched.py
@@ -1,11 +1,9 @@
 import queue
 import sched
+import threading
 import time
 import unittest
-try:
-    import threading
-except ImportError:
-    threading = None
+
 
 TIMEOUT = 10
 
@@ -58,7 +56,6 @@ class TestCase(unittest.TestCase):
         scheduler.run()
         self.assertEqual(l, [0.01, 0.02, 0.03, 0.04, 0.05])
 
-    @unittest.skipUnless(threading, 'Threading required for this test.')
     def test_enter_concurrent(self):
         q = queue.Queue()
         fun = q.put
@@ -113,7 +110,6 @@ class TestCase(unittest.TestCase):
         scheduler.run()
         self.assertEqual(l, [0.02, 0.03, 0.04])
 
-    @unittest.skipUnless(threading, 'Threading required for this test.')
     def test_cancel_concurrent(self):
         q = queue.Queue()
         fun = q.put
diff --git a/Lib/test/test_signal.py b/Lib/test/test_signal.py
index 0e1d067..dc048e5 100644
--- a/Lib/test/test_signal.py
+++ b/Lib/test/test_signal.py
@@ -5,15 +5,12 @@ import socket
 import statistics
 import subprocess
 import sys
+import threading
 import time
 import unittest
 from test import support
 from test.support.script_helper import assert_python_ok, spawn_python
 try:
-    import threading
-except ImportError:
-    threading = None
-try:
     import _testcapi
 except ImportError:
     _testcapi = None
@@ -21,7 +18,6 @@ except ImportError:
 
 class GenericTests(unittest.TestCase):
 
-    @unittest.skipIf(threading is None, "test needs threading module")
     def test_enums(self):
         for name in dir(signal):
             sig = getattr(signal, name)
@@ -807,7 +803,6 @@ class PendingSignalsTests(unittest.TestCase):
                          'need signal.sigwait()')
     @unittest.skipUnless(hasattr(signal, 'pthread_sigmask'),
                          'need signal.pthread_sigmask()')
-    @unittest.skipIf(threading is None, "test needs threading module")
     def test_sigwait_thread(self):
         # Check that calling sigwait() from a thread doesn't suspend the whole
         # process. A new interpreter is spawned to avoid problems when mixing
diff --git a/Lib/test/test_smtplib.py b/Lib/test/test_smtplib.py
index 28539f3..42f4266 100644
--- a/Lib/test/test_smtplib.py
+++ b/Lib/test/test_smtplib.py
@@ -15,14 +15,11 @@ import time
 import select
 import errno
 import textwrap
+import threading
 
 import unittest
 from test import support, mock_socket
 
-try:
-    import threading
-except ImportError:
-    threading = None
 
 HOST = support.HOST
 
@@ -191,7 +188,6 @@ MSG_END = '------------ END MESSAGE ------------\n'
 # test server times out, causing the test to fail.
 
 # Test behavior of smtpd.DebuggingServer
-@unittest.skipUnless(threading, 'Threading required for this test.')
 class DebuggingServerTests(unittest.TestCase):
 
     maxDiff = None
@@ -570,7 +566,6 @@ class NonConnectingTests(unittest.TestCase):
 
 
 # test response of client to a non-successful HELO message
-@unittest.skipUnless(threading, 'Threading required for this test.')
 class BadHELOServerTests(unittest.TestCase):
 
     def setUp(self):
@@ -590,7 +585,6 @@ class BadHELOServerTests(unittest.TestCase):
                             HOST, self.port, 'localhost', 3)
 
 
-@unittest.skipUnless(threading, 'Threading required for this test.')
 class TooLongLineTests(unittest.TestCase):
     respdata = b'250 OK' + (b'.' * smtplib._MAXLINE * 2) + b'\n'
 
@@ -835,7 +829,6 @@ class SimSMTPServer(smtpd.SMTPServer):
 
 # Test various SMTP & ESMTP commands/behaviors that require a simulated server
 # (i.e., something with more features than DebuggingServer)
-@unittest.skipUnless(threading, 'Threading required for this test.')
 class SMTPSimTests(unittest.TestCase):
 
     def setUp(self):
@@ -1091,7 +1084,6 @@ class SimSMTPUTF8Server(SimSMTPServer):
         self.last_rcpt_options = rcpt_options
 
 
-@unittest.skipUnless(threading, 'Threading required for this test.')
 class SMTPUTF8SimTests(unittest.TestCase):
 
     maxDiff = None
@@ -1227,7 +1219,6 @@ class SimSMTPAUTHInitialResponseServer(SimSMTPServer):
     channel_class = SimSMTPAUTHInitialResponseChannel
 
 
-@unittest.skipUnless(threading, 'Threading required for this test.')
 class SMTPAUTHInitialResponseSimTests(unittest.TestCase):
     def setUp(self):
         self.real_getfqdn = socket.getfqdn
diff --git a/Lib/test/test_socket.py b/Lib/test/test_socket.py
index 50016ab..27d9d49 100644
--- a/Lib/test/test_socket.py
+++ b/Lib/test/test_socket.py
@@ -21,6 +21,8 @@ import pickle
 import struct
 import random
 import string
+import _thread as thread
+import threading
 try:
     import multiprocessing
 except ImportError:
@@ -36,12 +38,6 @@ MSG = 'Michael Gilfix was here\u1234\r\n'.encode('utf-8') ## test unicode string
 VSOCKPORT = 1234
 
 try:
-    import _thread as thread
-    import threading
-except ImportError:
-    thread = None
-    threading = None
-try:
     import _socket
 except ImportError:
     _socket = None
@@ -143,18 +139,17 @@ class ThreadSafeCleanupTestCase(unittest.TestCase):
     with a recursive lock.
     """
 
-    if threading:
-        def __init__(self, *args, **kwargs):
-            super().__init__(*args, **kwargs)
-            self._cleanup_lock = threading.RLock()
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self._cleanup_lock = threading.RLock()
 
-        def addCleanup(self, *args, **kwargs):
-            with self._cleanup_lock:
-                return super().addCleanup(*args, **kwargs)
+    def addCleanup(self, *args, **kwargs):
+        with self._cleanup_lock:
+            return super().addCleanup(*args, **kwargs)
 
-        def doCleanups(self, *args, **kwargs):
-            with self._cleanup_lock:
-                return super().doCleanups(*args, **kwargs)
+    def doCleanups(self, *args, **kwargs):
+        with self._cleanup_lock:
+            return super().doCleanups(*args, **kwargs)
 
 class SocketCANTest(unittest.TestCase):
 
@@ -407,7 +402,6 @@ class ThreadedRDSSocketTest(SocketRDSTest, ThreadableTest):
         ThreadableTest.clientTearDown(self)
 
 @unittest.skipIf(fcntl is None, "need fcntl")
-@unittest.skipUnless(thread, 'Threading required for this test.')
 @unittest.skipUnless(HAVE_SOCKET_VSOCK,
           'VSOCK sockets required for this test.')
 @unittest.skipUnless(get_cid() != 2,
@@ -1684,7 +1678,6 @@ class BasicCANTest(unittest.TestCase):
 
 
 @unittest.skipUnless(HAVE_SOCKET_CAN, 'SocketCan required for this test.')
-@unittest.skipUnless(thread, 'Threading required for this test.')
 class CANTest(ThreadedCANSocketTest):
 
     def __init__(self, methodName='runTest'):
@@ -1838,7 +1831,6 @@ class BasicRDSTest(unittest.TestCase):
 
 
 @unittest.skipUnless(HAVE_SOCKET_RDS, 'RDS sockets required for this test.')
-@unittest.skipUnless(thread, 'Threading required for this test.')
 class RDSTest(ThreadedRDSSocketTest):
 
     def __init__(self, methodName='runTest'):
@@ -1977,7 +1969,7 @@ class BasicVSOCKTest(unittest.TestCase):
                              s.getsockopt(socket.AF_VSOCK,
                              socket.SO_VM_SOCKETS_BUFFER_MIN_SIZE))
 
-@unittest.skipUnless(thread, 'Threading required for this test.')
+
 class BasicTCPTest(SocketConnectedTest):
 
     def __init__(self, methodName='runTest'):
@@ -2100,7 +2092,7 @@ class BasicTCPTest(SocketConnectedTest):
     def _testDetach(self):
         self.serv_conn.send(MSG)
 
-@unittest.skipUnless(thread, 'Threading required for this test.')
+
 class BasicUDPTest(ThreadedUDPSocketTest):
 
     def __init__(self, methodName='runTest'):
@@ -3697,17 +3689,14 @@ class SendrecvmsgUDPTestBase(SendrecvmsgDgramFlagsBase,
     pass
 
 @requireAttrs(socket.socket, "sendmsg")
-@unittest.skipUnless(thread, 'Threading required for this test.')
 class SendmsgUDPTest(SendmsgConnectionlessTests, SendrecvmsgUDPTestBase):
     pass
 
 @requireAttrs(socket.socket, "recvmsg")
-@unittest.skipUnless(thread, 'Threading required for this test.')
 class RecvmsgUDPTest(RecvmsgTests, SendrecvmsgUDPTestBase):
     pass
 
 @requireAttrs(socket.socket, "recvmsg_into")
-@unittest.skipUnless(thread, 'Threading required for this test.')
 class RecvmsgIntoUDPTest(RecvmsgIntoTests, SendrecvmsgUDPTestBase):
     pass
 
@@ -3724,21 +3713,18 @@ class SendrecvmsgUDP6TestBase(SendrecvmsgDgramFlagsBase,
 @requireAttrs(socket.socket, "sendmsg")
 @unittest.skipUnless(support.IPV6_ENABLED, 'IPv6 required for this test.')
 @requireSocket("AF_INET6", "SOCK_DGRAM")
-@unittest.skipUnless(thread, 'Threading required for this test.')
 class SendmsgUDP6Test(SendmsgConnectionlessTests, SendrecvmsgUDP6TestBase):
     pass
 
 @requireAttrs(socket.socket, "recvmsg")
 @unittest.skipUnless(support.IPV6_ENABLED, 'IPv6 required for this test.')
 @requireSocket("AF_INET6", "SOCK_DGRAM")
-@unittest.skipUnless(thread, 'Threading required for this test.')
 class RecvmsgUDP6Test(RecvmsgTests, SendrecvmsgUDP6TestBase):
     pass
 
 @requireAttrs(socket.socket, "recvmsg_into")
 @unittest.skipUnless(support.IPV6_ENABLED, 'IPv6 required for this test.')
 @requireSocket("AF_INET6", "SOCK_DGRAM")
-@unittest.skipUnless(thread, 'Threading required for this test.')
 class RecvmsgIntoUDP6Test(RecvmsgIntoTests, SendrecvmsgUDP6TestBase):
     pass
 
@@ -3746,7 +3732,6 @@ class RecvmsgIntoUDP6Test(RecvmsgIntoTests, SendrecvmsgUDP6TestBase):
 @unittest.skipUnless(support.IPV6_ENABLED, 'IPv6 required for this test.')
 @requireAttrs(socket, "IPPROTO_IPV6")
 @requireSocket("AF_INET6", "SOCK_DGRAM")
-@unittest.skipUnless(thread, 'Threading required for this test.')
 class RecvmsgRFC3542AncillaryUDP6Test(RFC3542AncillaryTest,
                                       SendrecvmsgUDP6TestBase):
     pass
@@ -3755,7 +3740,6 @@ class RecvmsgRFC3542AncillaryUDP6Test(RFC3542AncillaryTest,
 @unittest.skipUnless(support.IPV6_ENABLED, 'IPv6 required for this test.')
 @requireAttrs(socket, "IPPROTO_IPV6")
 @requireSocket("AF_INET6", "SOCK_DGRAM")
-@unittest.skipUnless(thread, 'Threading required for this test.')
 class RecvmsgIntoRFC3542AncillaryUDP6Test(RecvmsgIntoMixin,
                                           RFC3542AncillaryTest,
                                           SendrecvmsgUDP6TestBase):
@@ -3767,18 +3751,15 @@ class SendrecvmsgTCPTestBase(SendrecvmsgConnectedBase,
     pass
 
 @requireAttrs(socket.socket, "sendmsg")
-@unittest.skipUnless(thread, 'Threading required for this test.')
 class SendmsgTCPTest(SendmsgStreamTests, SendrecvmsgTCPTestBase):
     pass
 
 @requireAttrs(socket.socket, "recvmsg")
-@unittest.skipUnless(thread, 'Threading required for this test.')
 class RecvmsgTCPTest(RecvmsgTests, RecvmsgGenericStreamTests,
                      SendrecvmsgTCPTestBase):
     pass
 
 @requireAttrs(socket.socket, "recvmsg_into")
-@unittest.skipUnless(thread, 'Threading required for this test.')
 class RecvmsgIntoTCPTest(RecvmsgIntoTests, RecvmsgGenericStreamTests,
                          SendrecvmsgTCPTestBase):
     pass
@@ -3791,13 +3772,11 @@ class SendrecvmsgSCTPStreamTestBase(SendrecvmsgSCTPFlagsBase,
 
 @requireAttrs(socket.socket, "sendmsg")
 @requireSocket("AF_INET", "SOCK_STREAM", "IPPROTO_SCTP")
-@unittest.skipUnless(thread, 'Threading required for this test.')
 class SendmsgSCTPStreamTest(SendmsgStreamTests, SendrecvmsgSCTPStreamTestBase):
     pass
 
 @requireAttrs(socket.socket, "recvmsg")
 @requireSocket("AF_INET", "SOCK_STREAM", "IPPROTO_SCTP")
-@unittest.skipUnless(thread, 'Threading required for this test.')
 class RecvmsgSCTPStreamTest(RecvmsgTests, RecvmsgGenericStreamTests,
                             SendrecvmsgSCTPStreamTestBase):
 
@@ -3811,7 +3790,6 @@ class RecvmsgSCTPStreamTest(RecvmsgTests, RecvmsgGenericStreamTests,
 
 @requireAttrs(socket.socket, "recvmsg_into")
 @requireSocket("AF_INET", "SOCK_STREAM", "IPPROTO_SCTP")
-@unittest.skipUnless(thread, 'Threading required for this test.')
 class RecvmsgIntoSCTPStreamTest(RecvmsgIntoTests, RecvmsgGenericStreamTests,
                                 SendrecvmsgSCTPStreamTestBase):
 
@@ -3830,33 +3808,28 @@ class SendrecvmsgUnixStreamTestBase(SendrecvmsgConnectedBase,
 
 @requireAttrs(socket.socket, "sendmsg")
 @requireAttrs(socket, "AF_UNIX")
-@unittest.skipUnless(thread, 'Threading required for this test.')
 class SendmsgUnixStreamTest(SendmsgStreamTests, SendrecvmsgUnixStreamTestBase):
     pass
 
 @requireAttrs(socket.socket, "recvmsg")
 @requireAttrs(socket, "AF_UNIX")
-@unittest.skipUnless(thread, 'Threading required for this test.')
 class RecvmsgUnixStreamTest(RecvmsgTests, RecvmsgGenericStreamTests,
                             SendrecvmsgUnixStreamTestBase):
     pass
 
 @requireAttrs(socket.socket, "recvmsg_into")
 @requireAttrs(socket, "AF_UNIX")
-@unittest.skipUnless(thread, 'Threading required for this test.')
 class RecvmsgIntoUnixStreamTest(RecvmsgIntoTests, RecvmsgGenericStreamTests,
                                 SendrecvmsgUnixStreamTestBase):
     pass
 
 @requireAttrs(socket.socket, "sendmsg", "recvmsg")
 @requireAttrs(socket, "AF_UNIX", "SOL_SOCKET", "SCM_RIGHTS")
-@unittest.skipUnless(thread, 'Threading required for this test.')
 class RecvmsgSCMRightsStreamTest(SCMRightsTest, SendrecvmsgUnixStreamTestBase):
     pass
 
 @requireAttrs(socket.socket, "sendmsg", "recvmsg_into")
 @requireAttrs(socket, "AF_UNIX", "SOL_SOCKET", "SCM_RIGHTS")
-@unittest.skipUnless(thread, 'Threading required for this test.')
 class RecvmsgIntoSCMRightsStreamTest(RecvmsgIntoMixin, SCMRightsTest,
                                      SendrecvmsgUnixStreamTestBase):
     pass
@@ -3944,7 +3917,6 @@ class InterruptedRecvTimeoutTest(InterruptedTimeoutBase, UDPTestBase):
 @requireAttrs(signal, "siginterrupt")
 @unittest.skipUnless(hasattr(signal, "alarm") or hasattr(signal, "setitimer"),
                      "Don't have signal.alarm or signal.setitimer")
-@unittest.skipUnless(thread, 'Threading required for this test.')
 class InterruptedSendTimeoutTest(InterruptedTimeoutBase,
                                  ThreadSafeCleanupTestCase,
                                  SocketListeningTestMixin, TCPTestBase):
@@ -3997,7 +3969,6 @@ class InterruptedSendTimeoutTest(InterruptedTimeoutBase,
         self.checkInterruptedSend(self.serv_conn.sendmsg, [b"a"*512])
 
 
-@unittest.skipUnless(thread, 'Threading required for this test.')
 class TCPCloserTest(ThreadedTCPSocketTest):
 
     def testClose(self):
@@ -4017,7 +3988,7 @@ class TCPCloserTest(ThreadedTCPSocketTest):
         self.cli.connect((HOST, self.port))
         time.sleep(1.0)
 
-@unittest.skipUnless(thread, 'Threading required for this test.')
+
 class BasicSocketPairTest(SocketPairTest):
 
     def __init__(self, methodName='runTest'):
@@ -4052,7 +4023,7 @@ class BasicSocketPairTest(SocketPairTest):
         msg = self.cli.recv(1024)
         self.assertEqual(msg, MSG)
 
-@unittest.skipUnless(thread, 'Threading required for this test.')
+
 class NonBlockingTCPTests(ThreadedTCPSocketTest):
 
     def __init__(self, methodName='runTest'):
@@ -4180,7 +4151,7 @@ class NonBlockingTCPTests(ThreadedTCPSocketTest):
         time.sleep(0.1)
         self.cli.send(MSG)
 
-@unittest.skipUnless(thread, 'Threading required for this test.')
+
 class FileObjectClassTestCase(SocketConnectedTest):
     """Unit tests for the object returned by socket.makefile()
 
@@ -4564,7 +4535,6 @@ class NetworkConnectionNoServer(unittest.TestCase):
                 socket.create_connection((HOST, 1234))
 
 
-@unittest.skipUnless(thread, 'Threading required for this test.')
 class NetworkConnectionAttributesTest(SocketTCPTest, ThreadableTest):
 
     def __init__(self, methodName='runTest'):
@@ -4633,7 +4603,7 @@ class NetworkConnectionAttributesTest(SocketTCPTest, ThreadableTest):
         self.addCleanup(self.cli.close)
         self.assertEqual(self.cli.gettimeout(), 30)
 
-@unittest.skipUnless(thread, 'Threading required for this test.')
+
 class NetworkConnectionBehaviourTest(SocketTCPTest, ThreadableTest):
 
     def __init__(self, methodName='runTest'):
@@ -4877,7 +4847,7 @@ class TestUnixDomain(unittest.TestCase):
         self.addCleanup(support.unlink, path)
         self.assertEqual(self.sock.getsockname(), path)
 
-@unittest.skipUnless(thread, 'Threading required for this test.')
+
 class BufferIOTest(SocketConnectedTest):
     """
     Test the buffer versions of socket.recv() and socket.send().
@@ -5050,7 +5020,6 @@ class TIPCThreadableTest(unittest.TestCase, ThreadableTest):
         self.cli.close()
 
 
-@unittest.skipUnless(thread, 'Threading required for this test.')
 class ContextManagersTest(ThreadedTCPSocketTest):
 
     def _testSocketClass(self):
@@ -5312,7 +5281,6 @@ class TestSocketSharing(SocketTCPTest):
                     source.close()
 
 
-@unittest.skipUnless(thread, 'Threading required for this test.')
 class SendfileUsingSendTest(ThreadedTCPSocketTest):
     """
     Test the send() implementation of socket.sendfile().
@@ -5570,7 +5538,6 @@ class SendfileUsingSendTest(ThreadedTCPSocketTest):
                                        meth, file, count=-1)
 
 
-@unittest.skipUnless(thread, 'Threading required for this test.')
 @unittest.skipUnless(hasattr(os, "sendfile"),
                      'os.sendfile() required for this test.')
 class SendfileUsingSendfileTest(SendfileUsingSendTest):
diff --git a/Lib/test/test_socketserver.py b/Lib/test/test_socketserver.py
index 3d93566..a23373f 100644
--- a/Lib/test/test_socketserver.py
+++ b/Lib/test/test_socketserver.py
@@ -9,15 +9,13 @@ import select
 import signal
 import socket
 import tempfile
+import threading
 import unittest
 import socketserver
 
 import test.support
 from test.support import reap_children, reap_threads, verbose
-try:
-    import threading
-except ImportError:
-    threading = None
+
 
 test.support.requires("network")
 
@@ -68,7 +66,6 @@ def simple_subprocess(testcase):
     testcase.assertEqual(72 << 8, status)
 
 
-@unittest.skipUnless(threading, 'Threading required for this test.')
 class SocketServerTest(unittest.TestCase):
     """Test all socket servers."""
 
@@ -306,12 +303,10 @@ class ErrorHandlerTest(unittest.TestCase):
             BaseErrorTestServer(SystemExit)
         self.check_result(handled=False)
 
-    @unittest.skipUnless(threading, 'Threading required for this test.')
     def test_threading_handled(self):
         ThreadingErrorTestServer(ValueError)
         self.check_result(handled=True)
 
-    @unittest.skipUnless(threading, 'Threading required for this test.')
     def test_threading_not_handled(self):
         ThreadingErrorTestServer(SystemExit)
         self.check_result(handled=False)
@@ -396,7 +391,6 @@ class SocketWriterTest(unittest.TestCase):
         self.assertIsInstance(server.wfile, io.BufferedIOBase)
         self.assertEqual(server.wfile_fileno, server.request_fileno)
 
-    @unittest.skipUnless(threading, 'Threading required for this test.')
     def test_write(self):
         # Test that wfile.write() sends data immediately, and that it does
         # not truncate sends when interrupted by a Unix signal
diff --git a/Lib/test/test_ssl.py b/Lib/test/test_ssl.py
index 16cad9d..89b4609 100644
--- a/Lib/test/test_ssl.py
+++ b/Lib/test/test_ssl.py
@@ -12,6 +12,7 @@ import os
 import errno
 import pprint
 import urllib.request
+import threading
 import traceback
 import asyncore
 import weakref
@@ -20,12 +21,6 @@ import functools
 
 ssl = support.import_module("ssl")
 
-try:
-    import threading
-except ImportError:
-    _have_threads = False
-else:
-    _have_threads = True
 
 PROTOCOLS = sorted(ssl._PROTOCOL_NAMES)
 HOST = support.HOST
@@ -1468,7 +1463,6 @@ class MemoryBIOTests(unittest.TestCase):
         self.assertRaises(TypeError, bio.write, 1)
 
 
-@unittest.skipUnless(_have_threads, "Needs threading module")
 class SimpleBackgroundTests(unittest.TestCase):
 
     """Tests that connect to a simple server running in the background"""
@@ -1828,1744 +1822,1743 @@ def _test_get_server_certificate_fail(test, host, port):
         test.fail("Got server certificate %s for %s:%s!" % (pem, host, port))
 
 
-if _have_threads:
-    from test.ssl_servers import make_https_server
+from test.ssl_servers import make_https_server
 
-    class ThreadedEchoServer(threading.Thread):
+class ThreadedEchoServer(threading.Thread):
 
-        class ConnectionHandler(threading.Thread):
+    class ConnectionHandler(threading.Thread):
 
-            """A mildly complicated class, because we want it to work both
-            with and without the SSL wrapper around the socket connection, so
-            that we can test the STARTTLS functionality."""
+        """A mildly complicated class, because we want it to work both
+        with and without the SSL wrapper around the socket connection, so
+        that we can test the STARTTLS functionality."""
 
-            def __init__(self, server, connsock, addr):
-                self.server = server
+        def __init__(self, server, connsock, addr):
+            self.server = server
+            self.running = False
+            self.sock = connsock
+            self.addr = addr
+            self.sock.setblocking(1)
+            self.sslconn = None
+            threading.Thread.__init__(self)
+            self.daemon = True
+
+        def wrap_conn(self):
+            try:
+                self.sslconn = self.server.context.wrap_socket(
+                    self.sock, server_side=True)
+                self.server.selected_npn_protocols.append(self.sslconn.selected_npn_protocol())
+                self.server.selected_alpn_protocols.append(self.sslconn.selected_alpn_protocol())
+            except (ssl.SSLError, ConnectionResetError, OSError) as e:
+                # We treat ConnectionResetError as though it were an
+                # SSLError - OpenSSL on Ubuntu abruptly closes the
+                # connection when asked to use an unsupported protocol.
+                #
+                # OSError may occur with wrong protocols, e.g. both
+                # sides use PROTOCOL_TLS_SERVER.
+                #
+                # XXX Various errors can have happened here, for example
+                # a mismatching protocol version, an invalid certificate,
+                # or a low-level bug. This should be made more discriminating.
+                #
+                # bpo-31323: Store the exception as string to prevent
+                # a reference leak: server -> conn_errors -> exception
+                # -> traceback -> self (ConnectionHandler) -> server
+                self.server.conn_errors.append(str(e))
+                if self.server.chatty:
+                    handle_error("\n server:  bad connection attempt from " + repr(self.addr) + ":\n")
                 self.running = False
-                self.sock = connsock
-                self.addr = addr
-                self.sock.setblocking(1)
-                self.sslconn = None
-                threading.Thread.__init__(self)
-                self.daemon = True
-
-            def wrap_conn(self):
-                try:
-                    self.sslconn = self.server.context.wrap_socket(
-                        self.sock, server_side=True)
-                    self.server.selected_npn_protocols.append(self.sslconn.selected_npn_protocol())
-                    self.server.selected_alpn_protocols.append(self.sslconn.selected_alpn_protocol())
-                except (ssl.SSLError, ConnectionResetError, OSError) as e:
-                    # We treat ConnectionResetError as though it were an
-                    # SSLError - OpenSSL on Ubuntu abruptly closes the
-                    # connection when asked to use an unsupported protocol.
-                    #
-                    # OSError may occur with wrong protocols, e.g. both
-                    # sides use PROTOCOL_TLS_SERVER.
-                    #
-                    # XXX Various errors can have happened here, for example
-                    # a mismatching protocol version, an invalid certificate,
-                    # or a low-level bug. This should be made more discriminating.
-                    #
-                    # bpo-31323: Store the exception as string to prevent
-                    # a reference leak: server -> conn_errors -> exception
-                    # -> traceback -> self (ConnectionHandler) -> server
-                    self.server.conn_errors.append(str(e))
-                    if self.server.chatty:
-                        handle_error("\n server:  bad connection attempt from " + repr(self.addr) + ":\n")
-                    self.running = False
-                    self.server.stop()
-                    self.close()
-                    return False
-                else:
-                    self.server.shared_ciphers.append(self.sslconn.shared_ciphers())
-                    if self.server.context.verify_mode == ssl.CERT_REQUIRED:
-                        cert = self.sslconn.getpeercert()
-                        if support.verbose and self.server.chatty:
-                            sys.stdout.write(" client cert is " + pprint.pformat(cert) + "\n")
-                        cert_binary = self.sslconn.getpeercert(True)
-                        if support.verbose and self.server.chatty:
-                            sys.stdout.write(" cert binary is " + str(len(cert_binary)) + " bytes\n")
-                    cipher = self.sslconn.cipher()
+                self.server.stop()
+                self.close()
+                return False
+            else:
+                self.server.shared_ciphers.append(self.sslconn.shared_ciphers())
+                if self.server.context.verify_mode == ssl.CERT_REQUIRED:
+                    cert = self.sslconn.getpeercert()
                     if support.verbose and self.server.chatty:
-                        sys.stdout.write(" server: connection cipher is now " + str(cipher) + "\n")
-                        sys.stdout.write(" server: selected protocol is now "
-                                + str(self.sslconn.selected_npn_protocol()) + "\n")
-                    return True
-
-            def read(self):
-                if self.sslconn:
-                    return self.sslconn.read()
-                else:
-                    return self.sock.recv(1024)
+                        sys.stdout.write(" client cert is " + pprint.pformat(cert) + "\n")
+                    cert_binary = self.sslconn.getpeercert(True)
+                    if support.verbose and self.server.chatty:
+                        sys.stdout.write(" cert binary is " + str(len(cert_binary)) + " bytes\n")
+                cipher = self.sslconn.cipher()
+                if support.verbose and self.server.chatty:
+                    sys.stdout.write(" server: connection cipher is now " + str(cipher) + "\n")
+                    sys.stdout.write(" server: selected protocol is now "
+                            + str(self.sslconn.selected_npn_protocol()) + "\n")
+                return True
+
+        def read(self):
+            if self.sslconn:
+                return self.sslconn.read()
+            else:
+                return self.sock.recv(1024)
 
-            def write(self, bytes):
-                if self.sslconn:
-                    return self.sslconn.write(bytes)
-                else:
-                    return self.sock.send(bytes)
+        def write(self, bytes):
+            if self.sslconn:
+                return self.sslconn.write(bytes)
+            else:
+                return self.sock.send(bytes)
 
-            def close(self):
-                if self.sslconn:
-                    self.sslconn.close()
-                else:
-                    self.sock.close()
+        def close(self):
+            if self.sslconn:
+                self.sslconn.close()
+            else:
+                self.sock.close()
 
-            def run(self):
-                self.running = True
-                if not self.server.starttls_server:
-                    if not self.wrap_conn():
-                        return
-                while self.running:
-                    try:
-                        msg = self.read()
-                        stripped = msg.strip()
-                        if not stripped:
-                            # eof, so quit this handler
-                            self.running = False
-                            try:
-                                self.sock = self.sslconn.unwrap()
-                            except OSError:
-                                # Many tests shut the TCP connection down
-                                # without an SSL shutdown. This causes
-                                # unwrap() to raise OSError with errno=0!
-                                pass
-                            else:
-                                self.sslconn = None
-                            self.close()
-                        elif stripped == b'over':
-                            if support.verbose and self.server.connectionchatty:
-                                sys.stdout.write(" server: client closed connection\n")
-                            self.close()
-                            return
-                        elif (self.server.starttls_server and
-                              stripped == b'STARTTLS'):
-                            if support.verbose and self.server.connectionchatty:
-                                sys.stdout.write(" server: read STARTTLS from client, sending OK...\n")
-                            self.write(b"OK\n")
-                            if not self.wrap_conn():
-                                return
-                        elif (self.server.starttls_server and self.sslconn
-                              and stripped == b'ENDTLS'):
-                            if support.verbose and self.server.connectionchatty:
-                                sys.stdout.write(" server: read ENDTLS from client, sending OK...\n")
-                            self.write(b"OK\n")
+        def run(self):
+            self.running = True
+            if not self.server.starttls_server:
+                if not self.wrap_conn():
+                    return
+            while self.running:
+                try:
+                    msg = self.read()
+                    stripped = msg.strip()
+                    if not stripped:
+                        # eof, so quit this handler
+                        self.running = False
+                        try:
                             self.sock = self.sslconn.unwrap()
-                            self.sslconn = None
-                            if support.verbose and self.server.connectionchatty:
-                                sys.stdout.write(" server: connection is now unencrypted...\n")
-                        elif stripped == b'CB tls-unique':
-                            if support.verbose and self.server.connectionchatty:
-                                sys.stdout.write(" server: read CB tls-unique from client, sending our CB data...\n")
-                            data = self.sslconn.get_channel_binding("tls-unique")
-                            self.write(repr(data).encode("us-ascii") + b"\n")
+                        except OSError:
+                            # Many tests shut the TCP connection down
+                            # without an SSL shutdown. This causes
+                            # unwrap() to raise OSError with errno=0!
+                            pass
                         else:
-                            if (support.verbose and
-                                self.server.connectionchatty):
-                                ctype = (self.sslconn and "encrypted") or "unencrypted"
-                                sys.stdout.write(" server: read %r (%s), sending back %r (%s)...\n"
-                                                 % (msg, ctype, msg.lower(), ctype))
-                            self.write(msg.lower())
-                    except OSError:
-                        if self.server.chatty:
-                            handle_error("Test server failure:\n")
+                            self.sslconn = None
                         self.close()
-                        self.running = False
-                        # normally, we'd just stop here, but for the test
-                        # harness, we want to stop the server
-                        self.server.stop()
-
-        def __init__(self, certificate=None, ssl_version=None,
-                     certreqs=None, cacerts=None,
-                     chatty=True, connectionchatty=False, starttls_server=False,
-                     npn_protocols=None, alpn_protocols=None,
-                     ciphers=None, context=None):
-            if context:
-                self.context = context
-            else:
-                self.context = ssl.SSLContext(ssl_version
-                                              if ssl_version is not None
-                                              else ssl.PROTOCOL_TLSv1)
-                self.context.verify_mode = (certreqs if certreqs is not None
-                                            else ssl.CERT_NONE)
-                if cacerts:
-                    self.context.load_verify_locations(cacerts)
-                if certificate:
-                    self.context.load_cert_chain(certificate)
-                if npn_protocols:
-                    self.context.set_npn_protocols(npn_protocols)
-                if alpn_protocols:
-                    self.context.set_alpn_protocols(alpn_protocols)
-                if ciphers:
-                    self.context.set_ciphers(ciphers)
-            self.chatty = chatty
-            self.connectionchatty = connectionchatty
-            self.starttls_server = starttls_server
-            self.sock = socket.socket()
-            self.port = support.bind_port(self.sock)
-            self.flag = None
-            self.active = False
-            self.selected_npn_protocols = []
-            self.selected_alpn_protocols = []
-            self.shared_ciphers = []
-            self.conn_errors = []
-            threading.Thread.__init__(self)
-            self.daemon = True
-
-        def __enter__(self):
-            self.start(threading.Event())
-            self.flag.wait()
-            return self
-
-        def __exit__(self, *args):
-            self.stop()
-            self.join()
-
-        def start(self, flag=None):
-            self.flag = flag
-            threading.Thread.start(self)
+                    elif stripped == b'over':
+                        if support.verbose and self.server.connectionchatty:
+                            sys.stdout.write(" server: client closed connection\n")
+                        self.close()
+                        return
+                    elif (self.server.starttls_server and
+                          stripped == b'STARTTLS'):
+                        if support.verbose and self.server.connectionchatty:
+                            sys.stdout.write(" server: read STARTTLS from client, sending OK...\n")
+                        self.write(b"OK\n")
+                        if not self.wrap_conn():
+                            return
+                    elif (self.server.starttls_server and self.sslconn
+                          and stripped == b'ENDTLS'):
+                        if support.verbose and self.server.connectionchatty:
+                            sys.stdout.write(" server: read ENDTLS from client, sending OK...\n")
+                        self.write(b"OK\n")
+                        self.sock = self.sslconn.unwrap()
+                        self.sslconn = None
+                        if support.verbose and self.server.connectionchatty:
+                            sys.stdout.write(" server: connection is now unencrypted...\n")
+                    elif stripped == b'CB tls-unique':
+                        if support.verbose and self.server.connectionchatty:
+                            sys.stdout.write(" server: read CB tls-unique from client, sending our CB data...\n")
+                        data = self.sslconn.get_channel_binding("tls-unique")
+                        self.write(repr(data).encode("us-ascii") + b"\n")
+                    else:
+                        if (support.verbose and
+                            self.server.connectionchatty):
+                            ctype = (self.sslconn and "encrypted") or "unencrypted"
+                            sys.stdout.write(" server: read %r (%s), sending back %r (%s)...\n"
+                                             % (msg, ctype, msg.lower(), ctype))
+                        self.write(msg.lower())
+                except OSError:
+                    if self.server.chatty:
+                        handle_error("Test server failure:\n")
+                    self.close()
+                    self.running = False
+                    # normally, we'd just stop here, but for the test
+                    # harness, we want to stop the server
+                    self.server.stop()
 
-        def run(self):
-            self.sock.settimeout(0.05)
-            self.sock.listen()
-            self.active = True
-            if self.flag:
-                # signal an event
-                self.flag.set()
-            while self.active:
-                try:
-                    newconn, connaddr = self.sock.accept()
-                    if support.verbose and self.chatty:
-                        sys.stdout.write(' server:  new connection from '
-                                         + repr(connaddr) + '\n')
-                    handler = self.ConnectionHandler(self, newconn, connaddr)
-                    handler.start()
-                    handler.join()
-                except socket.timeout:
-                    pass
-                except KeyboardInterrupt:
-                    self.stop()
-            self.sock.close()
+    def __init__(self, certificate=None, ssl_version=None,
+                 certreqs=None, cacerts=None,
+                 chatty=True, connectionchatty=False, starttls_server=False,
+                 npn_protocols=None, alpn_protocols=None,
+                 ciphers=None, context=None):
+        if context:
+            self.context = context
+        else:
+            self.context = ssl.SSLContext(ssl_version
+                                          if ssl_version is not None
+                                          else ssl.PROTOCOL_TLSv1)
+            self.context.verify_mode = (certreqs if certreqs is not None
+                                        else ssl.CERT_NONE)
+            if cacerts:
+                self.context.load_verify_locations(cacerts)
+            if certificate:
+                self.context.load_cert_chain(certificate)
+            if npn_protocols:
+                self.context.set_npn_protocols(npn_protocols)
+            if alpn_protocols:
+                self.context.set_alpn_protocols(alpn_protocols)
+            if ciphers:
+                self.context.set_ciphers(ciphers)
+        self.chatty = chatty
+        self.connectionchatty = connectionchatty
+        self.starttls_server = starttls_server
+        self.sock = socket.socket()
+        self.port = support.bind_port(self.sock)
+        self.flag = None
+        self.active = False
+        self.selected_npn_protocols = []
+        self.selected_alpn_protocols = []
+        self.shared_ciphers = []
+        self.conn_errors = []
+        threading.Thread.__init__(self)
+        self.daemon = True
+
+    def __enter__(self):
+        self.start(threading.Event())
+        self.flag.wait()
+        return self
+
+    def __exit__(self, *args):
+        self.stop()
+        self.join()
+
+    def start(self, flag=None):
+        self.flag = flag
+        threading.Thread.start(self)
+
+    def run(self):
+        self.sock.settimeout(0.05)
+        self.sock.listen()
+        self.active = True
+        if self.flag:
+            # signal an event
+            self.flag.set()
+        while self.active:
+            try:
+                newconn, connaddr = self.sock.accept()
+                if support.verbose and self.chatty:
+                    sys.stdout.write(' server:  new connection from '
+                                     + repr(connaddr) + '\n')
+                handler = self.ConnectionHandler(self, newconn, connaddr)
+                handler.start()
+                handler.join()
+            except socket.timeout:
+                pass
+            except KeyboardInterrupt:
+                self.stop()
+        self.sock.close()
 
-        def stop(self):
-            self.active = False
+    def stop(self):
+        self.active = False
 
-    class AsyncoreEchoServer(threading.Thread):
+class AsyncoreEchoServer(threading.Thread):
 
-        # this one's based on asyncore.dispatcher
+    # this one's based on asyncore.dispatcher
 
-        class EchoServer (asyncore.dispatcher):
+    class EchoServer (asyncore.dispatcher):
 
-            class ConnectionHandler(asyncore.dispatcher_with_send):
+        class ConnectionHandler(asyncore.dispatcher_with_send):
 
-                def __init__(self, conn, certfile):
-                    self.socket = test_wrap_socket(conn, server_side=True,
-                                                  certfile=certfile,
-                                                  do_handshake_on_connect=False)
-                    asyncore.dispatcher_with_send.__init__(self, self.socket)
-                    self._ssl_accepting = True
-                    self._do_ssl_handshake()
+            def __init__(self, conn, certfile):
+                self.socket = test_wrap_socket(conn, server_side=True,
+                                              certfile=certfile,
+                                              do_handshake_on_connect=False)
+                asyncore.dispatcher_with_send.__init__(self, self.socket)
+                self._ssl_accepting = True
+                self._do_ssl_handshake()
 
-                def readable(self):
-                    if isinstance(self.socket, ssl.SSLSocket):
-                        while self.socket.pending() > 0:
-                            self.handle_read_event()
-                    return True
+            def readable(self):
+                if isinstance(self.socket, ssl.SSLSocket):
+                    while self.socket.pending() > 0:
+                        self.handle_read_event()
+                return True
 
-                def _do_ssl_handshake(self):
-                    try:
-                        self.socket.do_handshake()
-                    except (ssl.SSLWantReadError, ssl.SSLWantWriteError):
-                        return
-                    except ssl.SSLEOFError:
+            def _do_ssl_handshake(self):
+                try:
+                    self.socket.do_handshake()
+                except (ssl.SSLWantReadError, ssl.SSLWantWriteError):
+                    return
+                except ssl.SSLEOFError:
+                    return self.handle_close()
+                except ssl.SSLError:
+                    raise
+                except OSError as err:
+                    if err.args[0] == errno.ECONNABORTED:
                         return self.handle_close()
-                    except ssl.SSLError:
-                        raise
-                    except OSError as err:
-                        if err.args[0] == errno.ECONNABORTED:
-                            return self.handle_close()
-                    else:
-                        self._ssl_accepting = False
-
-                def handle_read(self):
-                    if self._ssl_accepting:
-                        self._do_ssl_handshake()
-                    else:
-                        data = self.recv(1024)
-                        if support.verbose:
-                            sys.stdout.write(" server:  read %s from client\n" % repr(data))
-                        if not data:
-                            self.close()
-                        else:
-                            self.send(data.lower())
+                else:
+                    self._ssl_accepting = False
 
-                def handle_close(self):
-                    self.close()
+            def handle_read(self):
+                if self._ssl_accepting:
+                    self._do_ssl_handshake()
+                else:
+                    data = self.recv(1024)
                     if support.verbose:
-                        sys.stdout.write(" server:  closed connection %s\n" % self.socket)
-
-                def handle_error(self):
-                    raise
-
-            def __init__(self, certfile):
-                self.certfile = certfile
-                sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
-                self.port = support.bind_port(sock, '')
-                asyncore.dispatcher.__init__(self, sock)
-                self.listen(5)
+                        sys.stdout.write(" server:  read %s from client\n" % repr(data))
+                    if not data:
+                        self.close()
+                    else:
+                        self.send(data.lower())
 
-            def handle_accepted(self, sock_obj, addr):
+            def handle_close(self):
+                self.close()
                 if support.verbose:
-                    sys.stdout.write(" server:  new connection from %s:%s\n" %addr)
-                self.ConnectionHandler(sock_obj, self.certfile)
+                    sys.stdout.write(" server:  closed connection %s\n" % self.socket)
 
             def handle_error(self):
                 raise
 
         def __init__(self, certfile):
-            self.flag = None
-            self.active = False
-            self.server = self.EchoServer(certfile)
-            self.port = self.server.port
-            threading.Thread.__init__(self)
-            self.daemon = True
+            self.certfile = certfile
+            sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+            self.port = support.bind_port(sock, '')
+            asyncore.dispatcher.__init__(self, sock)
+            self.listen(5)
 
-        def __str__(self):
-            return "<%s %s>" % (self.__class__.__name__, self.server)
+        def handle_accepted(self, sock_obj, addr):
+            if support.verbose:
+                sys.stdout.write(" server:  new connection from %s:%s\n" %addr)
+            self.ConnectionHandler(sock_obj, self.certfile)
 
-        def __enter__(self):
-            self.start(threading.Event())
-            self.flag.wait()
-            return self
+        def handle_error(self):
+            raise
 
-        def __exit__(self, *args):
-            if support.verbose:
-                sys.stdout.write(" cleanup: stopping server.\n")
-            self.stop()
-            if support.verbose:
-                sys.stdout.write(" cleanup: joining server thread.\n")
-            self.join()
-            if support.verbose:
-                sys.stdout.write(" cleanup: successfully joined.\n")
-            # make sure that ConnectionHandler is removed from socket_map
-            asyncore.close_all(ignore_all=True)
+    def __init__(self, certfile):
+        self.flag = None
+        self.active = False
+        self.server = self.EchoServer(certfile)
+        self.port = self.server.port
+        threading.Thread.__init__(self)
+        self.daemon = True
 
-        def start (self, flag=None):
-            self.flag = flag
-            threading.Thread.start(self)
+    def __str__(self):
+        return "<%s %s>" % (self.__class__.__name__, self.server)
 
-        def run(self):
-            self.active = True
-            if self.flag:
-                self.flag.set()
-            while self.active:
-                try:
-                    asyncore.loop(1)
-                except:
-                    pass
+    def __enter__(self):
+        self.start(threading.Event())
+        self.flag.wait()
+        return self
 
-        def stop(self):
-            self.active = False
-            self.server.close()
+    def __exit__(self, *args):
+        if support.verbose:
+            sys.stdout.write(" cleanup: stopping server.\n")
+        self.stop()
+        if support.verbose:
+            sys.stdout.write(" cleanup: joining server thread.\n")
+        self.join()
+        if support.verbose:
+            sys.stdout.write(" cleanup: successfully joined.\n")
+        # make sure that ConnectionHandler is removed from socket_map
+        asyncore.close_all(ignore_all=True)
+
+    def start (self, flag=None):
+        self.flag = flag
+        threading.Thread.start(self)
+
+    def run(self):
+        self.active = True
+        if self.flag:
+            self.flag.set()
+        while self.active:
+            try:
+                asyncore.loop(1)
+            except:
+                pass
 
-    def server_params_test(client_context, server_context, indata=b"FOO\n",
-                           chatty=True, connectionchatty=False, sni_name=None,
-                           session=None):
-        """
-        Launch a server, connect a client to it and try various reads
-        and writes.
-        """
-        stats = {}
-        server = ThreadedEchoServer(context=server_context,
-                                    chatty=chatty,
-                                    connectionchatty=False)
-        with server:
-            with client_context.wrap_socket(socket.socket(),
-                    server_hostname=sni_name, session=session) as s:
-                s.connect((HOST, server.port))
-                for arg in [indata, bytearray(indata), memoryview(indata)]:
-                    if connectionchatty:
-                        if support.verbose:
-                            sys.stdout.write(
-                                " client:  sending %r...\n" % indata)
-                    s.write(arg)
-                    outdata = s.read()
-                    if connectionchatty:
-                        if support.verbose:
-                            sys.stdout.write(" client:  read %r\n" % outdata)
-                    if outdata != indata.lower():
-                        raise AssertionError(
-                            "bad data <<%r>> (%d) received; expected <<%r>> (%d)\n"
-                            % (outdata[:20], len(outdata),
-                               indata[:20].lower(), len(indata)))
-                s.write(b"over\n")
+    def stop(self):
+        self.active = False
+        self.server.close()
+
+def server_params_test(client_context, server_context, indata=b"FOO\n",
+                       chatty=True, connectionchatty=False, sni_name=None,
+                       session=None):
+    """
+    Launch a server, connect a client to it and try various reads
+    and writes.
+    """
+    stats = {}
+    server = ThreadedEchoServer(context=server_context,
+                                chatty=chatty,
+                                connectionchatty=False)
+    with server:
+        with client_context.wrap_socket(socket.socket(),
+                server_hostname=sni_name, session=session) as s:
+            s.connect((HOST, server.port))
+            for arg in [indata, bytearray(indata), memoryview(indata)]:
                 if connectionchatty:
                     if support.verbose:
-                        sys.stdout.write(" client:  closing connection.\n")
-                stats.update({
-                    'compression': s.compression(),
-                    'cipher': s.cipher(),
-                    'peercert': s.getpeercert(),
-                    'client_alpn_protocol': s.selected_alpn_protocol(),
-                    'client_npn_protocol': s.selected_npn_protocol(),
-                    'version': s.version(),
-                    'session_reused': s.session_reused,
-                    'session': s.session,
-                })
-                s.close()
-            stats['server_alpn_protocols'] = server.selected_alpn_protocols
-            stats['server_npn_protocols'] = server.selected_npn_protocols
-            stats['server_shared_ciphers'] = server.shared_ciphers
-        return stats
+                        sys.stdout.write(
+                            " client:  sending %r...\n" % indata)
+                s.write(arg)
+                outdata = s.read()
+                if connectionchatty:
+                    if support.verbose:
+                        sys.stdout.write(" client:  read %r\n" % outdata)
+                if outdata != indata.lower():
+                    raise AssertionError(
+                        "bad data <<%r>> (%d) received; expected <<%r>> (%d)\n"
+                        % (outdata[:20], len(outdata),
+                           indata[:20].lower(), len(indata)))
+            s.write(b"over\n")
+            if connectionchatty:
+                if support.verbose:
+                    sys.stdout.write(" client:  closing connection.\n")
+            stats.update({
+                'compression': s.compression(),
+                'cipher': s.cipher(),
+                'peercert': s.getpeercert(),
+                'client_alpn_protocol': s.selected_alpn_protocol(),
+                'client_npn_protocol': s.selected_npn_protocol(),
+                'version': s.version(),
+                'session_reused': s.session_reused,
+                'session': s.session,
+            })
+            s.close()
+        stats['server_alpn_protocols'] = server.selected_alpn_protocols
+        stats['server_npn_protocols'] = server.selected_npn_protocols
+        stats['server_shared_ciphers'] = server.shared_ciphers
+    return stats
+
+def try_protocol_combo(server_protocol, client_protocol, expect_success,
+                       certsreqs=None, server_options=0, client_options=0):
+    """
+    Try to SSL-connect using *client_protocol* to *server_protocol*.
+    If *expect_success* is true, assert that the connection succeeds,
+    if it's false, assert that the connection fails.
+    Also, if *expect_success* is a string, assert that it is the protocol
+    version actually used by the connection.
+    """
+    if certsreqs is None:
+        certsreqs = ssl.CERT_NONE
+    certtype = {
+        ssl.CERT_NONE: "CERT_NONE",
+        ssl.CERT_OPTIONAL: "CERT_OPTIONAL",
+        ssl.CERT_REQUIRED: "CERT_REQUIRED",
+    }[certsreqs]
+    if support.verbose:
+        formatstr = (expect_success and " %s->%s %s\n") or " {%s->%s} %s\n"
+        sys.stdout.write(formatstr %
+                         (ssl.get_protocol_name(client_protocol),
+                          ssl.get_protocol_name(server_protocol),
+                          certtype))
+    client_context = ssl.SSLContext(client_protocol)
+    client_context.options |= client_options
+    server_context = ssl.SSLContext(server_protocol)
+    server_context.options |= server_options
+
+    # NOTE: we must enable "ALL" ciphers on the client, otherwise an
+    # SSLv23 client will send an SSLv3 hello (rather than SSLv2)
+    # starting from OpenSSL 1.0.0 (see issue #8322).
+    if client_context.protocol == ssl.PROTOCOL_SSLv23:
+        client_context.set_ciphers("ALL")
+
+    for ctx in (client_context, server_context):
+        ctx.verify_mode = certsreqs
+        ctx.load_cert_chain(CERTFILE)
+        ctx.load_verify_locations(CERTFILE)
+    try:
+        stats = server_params_test(client_context, server_context,
+                                   chatty=False, connectionchatty=False)
+    # Protocol mismatch can result in either an SSLError, or a
+    # "Connection reset by peer" error.
+    except ssl.SSLError:
+        if expect_success:
+            raise
+    except OSError as e:
+        if expect_success or e.errno != errno.ECONNRESET:
+            raise
+    else:
+        if not expect_success:
+            raise AssertionError(
+                "Client protocol %s succeeded with server protocol %s!"
+                % (ssl.get_protocol_name(client_protocol),
+                   ssl.get_protocol_name(server_protocol)))
+        elif (expect_success is not True
+              and expect_success != stats['version']):
+            raise AssertionError("version mismatch: expected %r, got %r"
+                                 % (expect_success, stats['version']))
 
-    def try_protocol_combo(server_protocol, client_protocol, expect_success,
-                           certsreqs=None, server_options=0, client_options=0):
-        """
-        Try to SSL-connect using *client_protocol* to *server_protocol*.
-        If *expect_success* is true, assert that the connection succeeds,
-        if it's false, assert that the connection fails.
-        Also, if *expect_success* is a string, assert that it is the protocol
-        version actually used by the connection.
-        """
-        if certsreqs is None:
-            certsreqs = ssl.CERT_NONE
-        certtype = {
-            ssl.CERT_NONE: "CERT_NONE",
-            ssl.CERT_OPTIONAL: "CERT_OPTIONAL",
-            ssl.CERT_REQUIRED: "CERT_REQUIRED",
-        }[certsreqs]
-        if support.verbose:
-            formatstr = (expect_success and " %s->%s %s\n") or " {%s->%s} %s\n"
-            sys.stdout.write(formatstr %
-                             (ssl.get_protocol_name(client_protocol),
-                              ssl.get_protocol_name(server_protocol),
-                              certtype))
-        client_context = ssl.SSLContext(client_protocol)
-        client_context.options |= client_options
-        server_context = ssl.SSLContext(server_protocol)
-        server_context.options |= server_options
-
-        # NOTE: we must enable "ALL" ciphers on the client, otherwise an
-        # SSLv23 client will send an SSLv3 hello (rather than SSLv2)
-        # starting from OpenSSL 1.0.0 (see issue #8322).
-        if client_context.protocol == ssl.PROTOCOL_SSLv23:
-            client_context.set_ciphers("ALL")
-
-        for ctx in (client_context, server_context):
-            ctx.verify_mode = certsreqs
-            ctx.load_cert_chain(CERTFILE)
-            ctx.load_verify_locations(CERTFILE)
-        try:
-            stats = server_params_test(client_context, server_context,
-                                       chatty=False, connectionchatty=False)
-        # Protocol mismatch can result in either an SSLError, or a
-        # "Connection reset by peer" error.
-        except ssl.SSLError:
-            if expect_success:
-                raise
-        except OSError as e:
-            if expect_success or e.errno != errno.ECONNRESET:
-                raise
-        else:
-            if not expect_success:
-                raise AssertionError(
-                    "Client protocol %s succeeded with server protocol %s!"
-                    % (ssl.get_protocol_name(client_protocol),
-                       ssl.get_protocol_name(server_protocol)))
-            elif (expect_success is not True
-                  and expect_success != stats['version']):
-                raise AssertionError("version mismatch: expected %r, got %r"
-                                     % (expect_success, stats['version']))
-
-
-    class ThreadedTests(unittest.TestCase):
-
-        @skip_if_broken_ubuntu_ssl
-        def test_echo(self):
-            """Basic test of an SSL client connecting to a server"""
-            if support.verbose:
-                sys.stdout.write("\n")
-            for protocol in PROTOCOLS:
-                if protocol in {ssl.PROTOCOL_TLS_CLIENT, ssl.PROTOCOL_TLS_SERVER}:
-                    continue
-                with self.subTest(protocol=ssl._PROTOCOL_NAMES[protocol]):
-                    context = ssl.SSLContext(protocol)
-                    context.load_cert_chain(CERTFILE)
-                    server_params_test(context, context,
-                                       chatty=True, connectionchatty=True)
 
-            client_context = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
-            client_context.load_verify_locations(SIGNING_CA)
-            server_context = ssl.SSLContext(ssl.PROTOCOL_TLS_SERVER)
-            # server_context.load_verify_locations(SIGNING_CA)
-            server_context.load_cert_chain(SIGNED_CERTFILE2)
+class ThreadedTests(unittest.TestCase):
 
-            with self.subTest(client=ssl.PROTOCOL_TLS_CLIENT, server=ssl.PROTOCOL_TLS_SERVER):
-                server_params_test(client_context=client_context,
-                                   server_context=server_context,
+    @skip_if_broken_ubuntu_ssl
+    def test_echo(self):
+        """Basic test of an SSL client connecting to a server"""
+        if support.verbose:
+            sys.stdout.write("\n")
+        for protocol in PROTOCOLS:
+            if protocol in {ssl.PROTOCOL_TLS_CLIENT, ssl.PROTOCOL_TLS_SERVER}:
+                continue
+            with self.subTest(protocol=ssl._PROTOCOL_NAMES[protocol]):
+                context = ssl.SSLContext(protocol)
+                context.load_cert_chain(CERTFILE)
+                server_params_test(context, context,
+                                   chatty=True, connectionchatty=True)
+
+        client_context = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
+        client_context.load_verify_locations(SIGNING_CA)
+        server_context = ssl.SSLContext(ssl.PROTOCOL_TLS_SERVER)
+        # server_context.load_verify_locations(SIGNING_CA)
+        server_context.load_cert_chain(SIGNED_CERTFILE2)
+
+        with self.subTest(client=ssl.PROTOCOL_TLS_CLIENT, server=ssl.PROTOCOL_TLS_SERVER):
+            server_params_test(client_context=client_context,
+                               server_context=server_context,
+                               chatty=True, connectionchatty=True,
+                               sni_name='fakehostname')
+
+        client_context.check_hostname = False
+        with self.subTest(client=ssl.PROTOCOL_TLS_SERVER, server=ssl.PROTOCOL_TLS_CLIENT):
+            with self.assertRaises(ssl.SSLError) as e:
+                server_params_test(client_context=server_context,
+                                   server_context=client_context,
                                    chatty=True, connectionchatty=True,
                                    sni_name='fakehostname')
+            self.assertIn('called a function you should not call',
+                          str(e.exception))
 
-            client_context.check_hostname = False
-            with self.subTest(client=ssl.PROTOCOL_TLS_SERVER, server=ssl.PROTOCOL_TLS_CLIENT):
-                with self.assertRaises(ssl.SSLError) as e:
-                    server_params_test(client_context=server_context,
-                                       server_context=client_context,
-                                       chatty=True, connectionchatty=True,
-                                       sni_name='fakehostname')
-                self.assertIn('called a function you should not call',
-                              str(e.exception))
-
-            with self.subTest(client=ssl.PROTOCOL_TLS_SERVER, server=ssl.PROTOCOL_TLS_SERVER):
-                with self.assertRaises(ssl.SSLError) as e:
-                    server_params_test(client_context=server_context,
-                                       server_context=server_context,
-                                       chatty=True, connectionchatty=True)
-                self.assertIn('called a function you should not call',
-                              str(e.exception))
+        with self.subTest(client=ssl.PROTOCOL_TLS_SERVER, server=ssl.PROTOCOL_TLS_SERVER):
+            with self.assertRaises(ssl.SSLError) as e:
+                server_params_test(client_context=server_context,
+                                   server_context=server_context,
+                                   chatty=True, connectionchatty=True)
+            self.assertIn('called a function you should not call',
+                          str(e.exception))
 
-            with self.subTest(client=ssl.PROTOCOL_TLS_CLIENT, server=ssl.PROTOCOL_TLS_CLIENT):
-                with self.assertRaises(ssl.SSLError) as e:
-                    server_params_test(client_context=server_context,
-                                       server_context=client_context,
-                                       chatty=True, connectionchatty=True)
-                self.assertIn('called a function you should not call',
-                              str(e.exception))
+        with self.subTest(client=ssl.PROTOCOL_TLS_CLIENT, server=ssl.PROTOCOL_TLS_CLIENT):
+            with self.assertRaises(ssl.SSLError) as e:
+                server_params_test(client_context=server_context,
+                                   server_context=client_context,
+                                   chatty=True, connectionchatty=True)
+            self.assertIn('called a function you should not call',
+                          str(e.exception))
 
 
-        def test_getpeercert(self):
+    def test_getpeercert(self):
+        if support.verbose:
+            sys.stdout.write("\n")
+        context = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
+        context.verify_mode = ssl.CERT_REQUIRED
+        context.load_verify_locations(CERTFILE)
+        context.load_cert_chain(CERTFILE)
+        server = ThreadedEchoServer(context=context, chatty=False)
+        with server:
+            s = context.wrap_socket(socket.socket(),
+                                    do_handshake_on_connect=False)
+            s.connect((HOST, server.port))
+            # getpeercert() raise ValueError while the handshake isn't
+            # done.
+            with self.assertRaises(ValueError):
+                s.getpeercert()
+            s.do_handshake()
+            cert = s.getpeercert()
+            self.assertTrue(cert, "Can't get peer certificate.")
+            cipher = s.cipher()
             if support.verbose:
-                sys.stdout.write("\n")
-            context = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
-            context.verify_mode = ssl.CERT_REQUIRED
-            context.load_verify_locations(CERTFILE)
-            context.load_cert_chain(CERTFILE)
-            server = ThreadedEchoServer(context=context, chatty=False)
-            with server:
-                s = context.wrap_socket(socket.socket(),
-                                        do_handshake_on_connect=False)
+                sys.stdout.write(pprint.pformat(cert) + '\n')
+                sys.stdout.write("Connection cipher is " + str(cipher) + '.\n')
+            if 'subject' not in cert:
+                self.fail("No subject field in certificate: %s." %
+                          pprint.pformat(cert))
+            if ((('organizationName', 'Python Software Foundation'),)
+                not in cert['subject']):
+                self.fail(
+                    "Missing or invalid 'organizationName' field in certificate subject; "
+                    "should be 'Python Software Foundation'.")
+            self.assertIn('notBefore', cert)
+            self.assertIn('notAfter', cert)
+            before = ssl.cert_time_to_seconds(cert['notBefore'])
+            after = ssl.cert_time_to_seconds(cert['notAfter'])
+            self.assertLess(before, after)
+            s.close()
+
+    @unittest.skipUnless(have_verify_flags(),
+                        "verify_flags need OpenSSL > 0.9.8")
+    def test_crl_check(self):
+        if support.verbose:
+            sys.stdout.write("\n")
+
+        server_context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
+        server_context.load_cert_chain(SIGNED_CERTFILE)
+
+        context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
+        context.verify_mode = ssl.CERT_REQUIRED
+        context.load_verify_locations(SIGNING_CA)
+        tf = getattr(ssl, "VERIFY_X509_TRUSTED_FIRST", 0)
+        self.assertEqual(context.verify_flags, ssl.VERIFY_DEFAULT | tf)
+
+        # VERIFY_DEFAULT should pass
+        server = ThreadedEchoServer(context=server_context, chatty=True)
+        with server:
+            with context.wrap_socket(socket.socket()) as s:
                 s.connect((HOST, server.port))
-                # getpeercert() raise ValueError while the handshake isn't
-                # done.
-                with self.assertRaises(ValueError):
-                    s.getpeercert()
-                s.do_handshake()
                 cert = s.getpeercert()
                 self.assertTrue(cert, "Can't get peer certificate.")
-                cipher = s.cipher()
-                if support.verbose:
-                    sys.stdout.write(pprint.pformat(cert) + '\n')
-                    sys.stdout.write("Connection cipher is " + str(cipher) + '.\n')
-                if 'subject' not in cert:
-                    self.fail("No subject field in certificate: %s." %
-                              pprint.pformat(cert))
-                if ((('organizationName', 'Python Software Foundation'),)
-                    not in cert['subject']):
-                    self.fail(
-                        "Missing or invalid 'organizationName' field in certificate subject; "
-                        "should be 'Python Software Foundation'.")
-                self.assertIn('notBefore', cert)
-                self.assertIn('notAfter', cert)
-                before = ssl.cert_time_to_seconds(cert['notBefore'])
-                after = ssl.cert_time_to_seconds(cert['notAfter'])
-                self.assertLess(before, after)
-                s.close()
 
-        @unittest.skipUnless(have_verify_flags(),
-                            "verify_flags need OpenSSL > 0.9.8")
-        def test_crl_check(self):
-            if support.verbose:
-                sys.stdout.write("\n")
+        # VERIFY_CRL_CHECK_LEAF without a loaded CRL file fails
+        context.verify_flags |= ssl.VERIFY_CRL_CHECK_LEAF
 
-            server_context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
-            server_context.load_cert_chain(SIGNED_CERTFILE)
-
-            context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
-            context.verify_mode = ssl.CERT_REQUIRED
-            context.load_verify_locations(SIGNING_CA)
-            tf = getattr(ssl, "VERIFY_X509_TRUSTED_FIRST", 0)
-            self.assertEqual(context.verify_flags, ssl.VERIFY_DEFAULT | tf)
-
-            # VERIFY_DEFAULT should pass
-            server = ThreadedEchoServer(context=server_context, chatty=True)
-            with server:
-                with context.wrap_socket(socket.socket()) as s:
+        server = ThreadedEchoServer(context=server_context, chatty=True)
+        with server:
+            with context.wrap_socket(socket.socket()) as s:
+                with self.assertRaisesRegex(ssl.SSLError,
+                                            "certificate verify failed"):
                     s.connect((HOST, server.port))
-                    cert = s.getpeercert()
-                    self.assertTrue(cert, "Can't get peer certificate.")
 
-            # VERIFY_CRL_CHECK_LEAF without a loaded CRL file fails
-            context.verify_flags |= ssl.VERIFY_CRL_CHECK_LEAF
+        # now load a CRL file. The CRL file is signed by the CA.
+        context.load_verify_locations(CRLFILE)
 
-            server = ThreadedEchoServer(context=server_context, chatty=True)
-            with server:
-                with context.wrap_socket(socket.socket()) as s:
-                    with self.assertRaisesRegex(ssl.SSLError,
-                                                "certificate verify failed"):
-                        s.connect((HOST, server.port))
+        server = ThreadedEchoServer(context=server_context, chatty=True)
+        with server:
+            with context.wrap_socket(socket.socket()) as s:
+                s.connect((HOST, server.port))
+                cert = s.getpeercert()
+                self.assertTrue(cert, "Can't get peer certificate.")
 
-            # now load a CRL file. The CRL file is signed by the CA.
-            context.load_verify_locations(CRLFILE)
+    def test_check_hostname(self):
+        if support.verbose:
+            sys.stdout.write("\n")
 
-            server = ThreadedEchoServer(context=server_context, chatty=True)
-            with server:
-                with context.wrap_socket(socket.socket()) as s:
-                    s.connect((HOST, server.port))
-                    cert = s.getpeercert()
-                    self.assertTrue(cert, "Can't get peer certificate.")
+        server_context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
+        server_context.load_cert_chain(SIGNED_CERTFILE)
 
-        def test_check_hostname(self):
-            if support.verbose:
-                sys.stdout.write("\n")
+        context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
+        context.verify_mode = ssl.CERT_REQUIRED
+        context.check_hostname = True
+        context.load_verify_locations(SIGNING_CA)
 
-            server_context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
-            server_context.load_cert_chain(SIGNED_CERTFILE)
-
-            context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
-            context.verify_mode = ssl.CERT_REQUIRED
-            context.check_hostname = True
-            context.load_verify_locations(SIGNING_CA)
-
-            # correct hostname should verify
-            server = ThreadedEchoServer(context=server_context, chatty=True)
-            with server:
-                with context.wrap_socket(socket.socket(),
-                                         server_hostname="localhost") as s:
+        # correct hostname should verify
+        server = ThreadedEchoServer(context=server_context, chatty=True)
+        with server:
+            with context.wrap_socket(socket.socket(),
+                                     server_hostname="localhost") as s:
+                s.connect((HOST, server.port))
+                cert = s.getpeercert()
+                self.assertTrue(cert, "Can't get peer certificate.")
+
+        # incorrect hostname should raise an exception
+        server = ThreadedEchoServer(context=server_context, chatty=True)
+        with server:
+            with context.wrap_socket(socket.socket(),
+                                     server_hostname="invalid") as s:
+                with self.assertRaisesRegex(ssl.CertificateError,
+                                            "hostname 'invalid' doesn't match 'localhost'"):
                     s.connect((HOST, server.port))
-                    cert = s.getpeercert()
-                    self.assertTrue(cert, "Can't get peer certificate.")
-
-            # incorrect hostname should raise an exception
-            server = ThreadedEchoServer(context=server_context, chatty=True)
-            with server:
-                with context.wrap_socket(socket.socket(),
-                                         server_hostname="invalid") as s:
-                    with self.assertRaisesRegex(ssl.CertificateError,
-                                                "hostname 'invalid' doesn't match 'localhost'"):
-                        s.connect((HOST, server.port))
-
-            # missing server_hostname arg should cause an exception, too
-            server = ThreadedEchoServer(context=server_context, chatty=True)
-            with server:
-                with socket.socket() as s:
-                    with self.assertRaisesRegex(ValueError,
-                                                "check_hostname requires server_hostname"):
-                        context.wrap_socket(s)
-
-        def test_wrong_cert(self):
-            """Connecting when the server rejects the client's certificate
-
-            Launch a server with CERT_REQUIRED, and check that trying to
-            connect to it with a wrong client certificate fails.
-            """
-            certfile = os.path.join(os.path.dirname(__file__) or os.curdir,
-                                       "wrongcert.pem")
-            server = ThreadedEchoServer(CERTFILE,
-                                        certreqs=ssl.CERT_REQUIRED,
-                                        cacerts=CERTFILE, chatty=False,
-                                        connectionchatty=False)
-            with server, \
-                    socket.socket() as sock, \
-                    test_wrap_socket(sock,
-                                        certfile=certfile,
-                                        ssl_version=ssl.PROTOCOL_TLSv1) as s:
+
+        # missing server_hostname arg should cause an exception, too
+        server = ThreadedEchoServer(context=server_context, chatty=True)
+        with server:
+            with socket.socket() as s:
+                with self.assertRaisesRegex(ValueError,
+                                            "check_hostname requires server_hostname"):
+                    context.wrap_socket(s)
+
+    def test_wrong_cert(self):
+        """Connecting when the server rejects the client's certificate
+
+        Launch a server with CERT_REQUIRED, and check that trying to
+        connect to it with a wrong client certificate fails.
+        """
+        certfile = os.path.join(os.path.dirname(__file__) or os.curdir,
+                                   "wrongcert.pem")
+        server = ThreadedEchoServer(CERTFILE,
+                                    certreqs=ssl.CERT_REQUIRED,
+                                    cacerts=CERTFILE, chatty=False,
+                                    connectionchatty=False)
+        with server, \
+                socket.socket() as sock, \
+                test_wrap_socket(sock,
+                                    certfile=certfile,
+                                    ssl_version=ssl.PROTOCOL_TLSv1) as s:
+            try:
+                # Expect either an SSL error about the server rejecting
+                # the connection, or a low-level connection reset (which
+                # sometimes happens on Windows)
+                s.connect((HOST, server.port))
+            except ssl.SSLError as e:
+                if support.verbose:
+                    sys.stdout.write("\nSSLError is %r\n" % e)
+            except OSError as e:
+                if e.errno != errno.ECONNRESET:
+                    raise
+                if support.verbose:
+                    sys.stdout.write("\nsocket.error is %r\n" % e)
+            else:
+                self.fail("Use of invalid cert should have failed!")
+
+    def test_rude_shutdown(self):
+        """A brutal shutdown of an SSL server should raise an OSError
+        in the client when attempting handshake.
+        """
+        listener_ready = threading.Event()
+        listener_gone = threading.Event()
+
+        s = socket.socket()
+        port = support.bind_port(s, HOST)
+
+        # `listener` runs in a thread.  It sits in an accept() until
+        # the main thread connects.  Then it rudely closes the socket,
+        # and sets Event `listener_gone` to let the main thread know
+        # the socket is gone.
+        def listener():
+            s.listen()
+            listener_ready.set()
+            newsock, addr = s.accept()
+            newsock.close()
+            s.close()
+            listener_gone.set()
+
+        def connector():
+            listener_ready.wait()
+            with socket.socket() as c:
+                c.connect((HOST, port))
+                listener_gone.wait()
                 try:
-                    # Expect either an SSL error about the server rejecting
-                    # the connection, or a low-level connection reset (which
-                    # sometimes happens on Windows)
-                    s.connect((HOST, server.port))
-                except ssl.SSLError as e:
-                    if support.verbose:
-                        sys.stdout.write("\nSSLError is %r\n" % e)
-                except OSError as e:
-                    if e.errno != errno.ECONNRESET:
-                        raise
-                    if support.verbose:
-                        sys.stdout.write("\nsocket.error is %r\n" % e)
+                    ssl_sock = test_wrap_socket(c)
+                except OSError:
+                    pass
                 else:
-                    self.fail("Use of invalid cert should have failed!")
+                    self.fail('connecting to closed SSL socket should have failed')
 
-        def test_rude_shutdown(self):
-            """A brutal shutdown of an SSL server should raise an OSError
-            in the client when attempting handshake.
-            """
-            listener_ready = threading.Event()
-            listener_gone = threading.Event()
+        t = threading.Thread(target=listener)
+        t.start()
+        try:
+            connector()
+        finally:
+            t.join()
 
-            s = socket.socket()
-            port = support.bind_port(s, HOST)
-
-            # `listener` runs in a thread.  It sits in an accept() until
-            # the main thread connects.  Then it rudely closes the socket,
-            # and sets Event `listener_gone` to let the main thread know
-            # the socket is gone.
-            def listener():
-                s.listen()
-                listener_ready.set()
-                newsock, addr = s.accept()
-                newsock.close()
-                s.close()
-                listener_gone.set()
-
-            def connector():
-                listener_ready.wait()
-                with socket.socket() as c:
-                    c.connect((HOST, port))
-                    listener_gone.wait()
-                    try:
-                        ssl_sock = test_wrap_socket(c)
-                    except OSError:
-                        pass
-                    else:
-                        self.fail('connecting to closed SSL socket should have failed')
+    @skip_if_broken_ubuntu_ssl
+    @unittest.skipUnless(hasattr(ssl, 'PROTOCOL_SSLv2'),
+                         "OpenSSL is compiled without SSLv2 support")
+    def test_protocol_sslv2(self):
+        """Connecting to an SSLv2 server with various client options"""
+        if support.verbose:
+            sys.stdout.write("\n")
+        try_protocol_combo(ssl.PROTOCOL_SSLv2, ssl.PROTOCOL_SSLv2, True)
+        try_protocol_combo(ssl.PROTOCOL_SSLv2, ssl.PROTOCOL_SSLv2, True, ssl.CERT_OPTIONAL)
+        try_protocol_combo(ssl.PROTOCOL_SSLv2, ssl.PROTOCOL_SSLv2, True, ssl.CERT_REQUIRED)
+        try_protocol_combo(ssl.PROTOCOL_SSLv2, ssl.PROTOCOL_SSLv23, False)
+        if hasattr(ssl, 'PROTOCOL_SSLv3'):
+            try_protocol_combo(ssl.PROTOCOL_SSLv2, ssl.PROTOCOL_SSLv3, False)
+        try_protocol_combo(ssl.PROTOCOL_SSLv2, ssl.PROTOCOL_TLSv1, False)
+        # SSLv23 client with specific SSL options
+        if no_sslv2_implies_sslv3_hello():
+            # No SSLv2 => client will use an SSLv3 hello on recent OpenSSLs
+            try_protocol_combo(ssl.PROTOCOL_SSLv2, ssl.PROTOCOL_SSLv23, False,
+                               client_options=ssl.OP_NO_SSLv2)
+        try_protocol_combo(ssl.PROTOCOL_SSLv2, ssl.PROTOCOL_SSLv23, False,
+                           client_options=ssl.OP_NO_SSLv3)
+        try_protocol_combo(ssl.PROTOCOL_SSLv2, ssl.PROTOCOL_SSLv23, False,
+                           client_options=ssl.OP_NO_TLSv1)
 
-            t = threading.Thread(target=listener)
-            t.start()
+    @skip_if_broken_ubuntu_ssl
+    def test_protocol_sslv23(self):
+        """Connecting to an SSLv23 server with various client options"""
+        if support.verbose:
+            sys.stdout.write("\n")
+        if hasattr(ssl, 'PROTOCOL_SSLv2'):
             try:
-                connector()
-            finally:
-                t.join()
+                try_protocol_combo(ssl.PROTOCOL_SSLv23, ssl.PROTOCOL_SSLv2, True)
+            except OSError as x:
+                # this fails on some older versions of OpenSSL (0.9.7l, for instance)
+                if support.verbose:
+                    sys.stdout.write(
+                        " SSL2 client to SSL23 server test unexpectedly failed:\n %s\n"
+                        % str(x))
+        if hasattr(ssl, 'PROTOCOL_SSLv3'):
+            try_protocol_combo(ssl.PROTOCOL_SSLv23, ssl.PROTOCOL_SSLv3, False)
+        try_protocol_combo(ssl.PROTOCOL_SSLv23, ssl.PROTOCOL_SSLv23, True)
+        try_protocol_combo(ssl.PROTOCOL_SSLv23, ssl.PROTOCOL_TLSv1, 'TLSv1')
+
+        if hasattr(ssl, 'PROTOCOL_SSLv3'):
+            try_protocol_combo(ssl.PROTOCOL_SSLv23, ssl.PROTOCOL_SSLv3, False, ssl.CERT_OPTIONAL)
+        try_protocol_combo(ssl.PROTOCOL_SSLv23, ssl.PROTOCOL_SSLv23, True, ssl.CERT_OPTIONAL)
+        try_protocol_combo(ssl.PROTOCOL_SSLv23, ssl.PROTOCOL_TLSv1, 'TLSv1', ssl.CERT_OPTIONAL)
+
+        if hasattr(ssl, 'PROTOCOL_SSLv3'):
+            try_protocol_combo(ssl.PROTOCOL_SSLv23, ssl.PROTOCOL_SSLv3, False, ssl.CERT_REQUIRED)
+        try_protocol_combo(ssl.PROTOCOL_SSLv23, ssl.PROTOCOL_SSLv23, True, ssl.CERT_REQUIRED)
+        try_protocol_combo(ssl.PROTOCOL_SSLv23, ssl.PROTOCOL_TLSv1, 'TLSv1', ssl.CERT_REQUIRED)
+
+        # Server with specific SSL options
+        if hasattr(ssl, 'PROTOCOL_SSLv3'):
+            try_protocol_combo(ssl.PROTOCOL_SSLv23, ssl.PROTOCOL_SSLv3, False,
+                           server_options=ssl.OP_NO_SSLv3)
+        # Will choose TLSv1
+        try_protocol_combo(ssl.PROTOCOL_SSLv23, ssl.PROTOCOL_SSLv23, True,
+                           server_options=ssl.OP_NO_SSLv2 | ssl.OP_NO_SSLv3)
+        try_protocol_combo(ssl.PROTOCOL_SSLv23, ssl.PROTOCOL_TLSv1, False,
+                           server_options=ssl.OP_NO_TLSv1)
+
+
+    @skip_if_broken_ubuntu_ssl
+    @unittest.skipUnless(hasattr(ssl, 'PROTOCOL_SSLv3'),
+                         "OpenSSL is compiled without SSLv3 support")
+    def test_protocol_sslv3(self):
+        """Connecting to an SSLv3 server with various client options"""
+        if support.verbose:
+            sys.stdout.write("\n")
+        try_protocol_combo(ssl.PROTOCOL_SSLv3, ssl.PROTOCOL_SSLv3, 'SSLv3')
+        try_protocol_combo(ssl.PROTOCOL_SSLv3, ssl.PROTOCOL_SSLv3, 'SSLv3', ssl.CERT_OPTIONAL)
+        try_protocol_combo(ssl.PROTOCOL_SSLv3, ssl.PROTOCOL_SSLv3, 'SSLv3', ssl.CERT_REQUIRED)
+        if hasattr(ssl, 'PROTOCOL_SSLv2'):
+            try_protocol_combo(ssl.PROTOCOL_SSLv3, ssl.PROTOCOL_SSLv2, False)
+        try_protocol_combo(ssl.PROTOCOL_SSLv3, ssl.PROTOCOL_SSLv23, False,
+                           client_options=ssl.OP_NO_SSLv3)
+        try_protocol_combo(ssl.PROTOCOL_SSLv3, ssl.PROTOCOL_TLSv1, False)
+        if no_sslv2_implies_sslv3_hello():
+            # No SSLv2 => client will use an SSLv3 hello on recent OpenSSLs
+            try_protocol_combo(ssl.PROTOCOL_SSLv3, ssl.PROTOCOL_SSLv23,
+                               False, client_options=ssl.OP_NO_SSLv2)
+
+    @skip_if_broken_ubuntu_ssl
+    def test_protocol_tlsv1(self):
+        """Connecting to a TLSv1 server with various client options"""
+        if support.verbose:
+            sys.stdout.write("\n")
+        try_protocol_combo(ssl.PROTOCOL_TLSv1, ssl.PROTOCOL_TLSv1, 'TLSv1')
+        try_protocol_combo(ssl.PROTOCOL_TLSv1, ssl.PROTOCOL_TLSv1, 'TLSv1', ssl.CERT_OPTIONAL)
+        try_protocol_combo(ssl.PROTOCOL_TLSv1, ssl.PROTOCOL_TLSv1, 'TLSv1', ssl.CERT_REQUIRED)
+        if hasattr(ssl, 'PROTOCOL_SSLv2'):
+            try_protocol_combo(ssl.PROTOCOL_TLSv1, ssl.PROTOCOL_SSLv2, False)
+        if hasattr(ssl, 'PROTOCOL_SSLv3'):
+            try_protocol_combo(ssl.PROTOCOL_TLSv1, ssl.PROTOCOL_SSLv3, False)
+        try_protocol_combo(ssl.PROTOCOL_TLSv1, ssl.PROTOCOL_SSLv23, False,
+                           client_options=ssl.OP_NO_TLSv1)
+
+    @skip_if_broken_ubuntu_ssl
+    @unittest.skipUnless(hasattr(ssl, "PROTOCOL_TLSv1_1"),
+                         "TLS version 1.1 not supported.")
+    def test_protocol_tlsv1_1(self):
+        """Connecting to a TLSv1.1 server with various client options.
+           Testing against older TLS versions."""
+        if support.verbose:
+            sys.stdout.write("\n")
+        try_protocol_combo(ssl.PROTOCOL_TLSv1_1, ssl.PROTOCOL_TLSv1_1, 'TLSv1.1')
+        if hasattr(ssl, 'PROTOCOL_SSLv2'):
+            try_protocol_combo(ssl.PROTOCOL_TLSv1_1, ssl.PROTOCOL_SSLv2, False)
+        if hasattr(ssl, 'PROTOCOL_SSLv3'):
+            try_protocol_combo(ssl.PROTOCOL_TLSv1_1, ssl.PROTOCOL_SSLv3, False)
+        try_protocol_combo(ssl.PROTOCOL_TLSv1_1, ssl.PROTOCOL_SSLv23, False,
+                           client_options=ssl.OP_NO_TLSv1_1)
+
+        try_protocol_combo(ssl.PROTOCOL_SSLv23, ssl.PROTOCOL_TLSv1_1, 'TLSv1.1')
+        try_protocol_combo(ssl.PROTOCOL_TLSv1_1, ssl.PROTOCOL_TLSv1, False)
+        try_protocol_combo(ssl.PROTOCOL_TLSv1, ssl.PROTOCOL_TLSv1_1, False)
 
-        @skip_if_broken_ubuntu_ssl
-        @unittest.skipUnless(hasattr(ssl, 'PROTOCOL_SSLv2'),
-                             "OpenSSL is compiled without SSLv2 support")
-        def test_protocol_sslv2(self):
-            """Connecting to an SSLv2 server with various client options"""
-            if support.verbose:
-                sys.stdout.write("\n")
-            try_protocol_combo(ssl.PROTOCOL_SSLv2, ssl.PROTOCOL_SSLv2, True)
-            try_protocol_combo(ssl.PROTOCOL_SSLv2, ssl.PROTOCOL_SSLv2, True, ssl.CERT_OPTIONAL)
-            try_protocol_combo(ssl.PROTOCOL_SSLv2, ssl.PROTOCOL_SSLv2, True, ssl.CERT_REQUIRED)
-            try_protocol_combo(ssl.PROTOCOL_SSLv2, ssl.PROTOCOL_SSLv23, False)
-            if hasattr(ssl, 'PROTOCOL_SSLv3'):
-                try_protocol_combo(ssl.PROTOCOL_SSLv2, ssl.PROTOCOL_SSLv3, False)
-            try_protocol_combo(ssl.PROTOCOL_SSLv2, ssl.PROTOCOL_TLSv1, False)
-            # SSLv23 client with specific SSL options
-            if no_sslv2_implies_sslv3_hello():
-                # No SSLv2 => client will use an SSLv3 hello on recent OpenSSLs
-                try_protocol_combo(ssl.PROTOCOL_SSLv2, ssl.PROTOCOL_SSLv23, False,
-                                   client_options=ssl.OP_NO_SSLv2)
-            try_protocol_combo(ssl.PROTOCOL_SSLv2, ssl.PROTOCOL_SSLv23, False,
-                               client_options=ssl.OP_NO_SSLv3)
-            try_protocol_combo(ssl.PROTOCOL_SSLv2, ssl.PROTOCOL_SSLv23, False,
-                               client_options=ssl.OP_NO_TLSv1)
 
-        @skip_if_broken_ubuntu_ssl
-        def test_protocol_sslv23(self):
-            """Connecting to an SSLv23 server with various client options"""
+    @skip_if_broken_ubuntu_ssl
+    @unittest.skipUnless(hasattr(ssl, "PROTOCOL_TLSv1_2"),
+                         "TLS version 1.2 not supported.")
+    def test_protocol_tlsv1_2(self):
+        """Connecting to a TLSv1.2 server with various client options.
+           Testing against older TLS versions."""
+        if support.verbose:
+            sys.stdout.write("\n")
+        try_protocol_combo(ssl.PROTOCOL_TLSv1_2, ssl.PROTOCOL_TLSv1_2, 'TLSv1.2',
+                           server_options=ssl.OP_NO_SSLv3|ssl.OP_NO_SSLv2,
+                           client_options=ssl.OP_NO_SSLv3|ssl.OP_NO_SSLv2,)
+        if hasattr(ssl, 'PROTOCOL_SSLv2'):
+            try_protocol_combo(ssl.PROTOCOL_TLSv1_2, ssl.PROTOCOL_SSLv2, False)
+        if hasattr(ssl, 'PROTOCOL_SSLv3'):
+            try_protocol_combo(ssl.PROTOCOL_TLSv1_2, ssl.PROTOCOL_SSLv3, False)
+        try_protocol_combo(ssl.PROTOCOL_TLSv1_2, ssl.PROTOCOL_SSLv23, False,
+                           client_options=ssl.OP_NO_TLSv1_2)
+
+        try_protocol_combo(ssl.PROTOCOL_SSLv23, ssl.PROTOCOL_TLSv1_2, 'TLSv1.2')
+        try_protocol_combo(ssl.PROTOCOL_TLSv1_2, ssl.PROTOCOL_TLSv1, False)
+        try_protocol_combo(ssl.PROTOCOL_TLSv1, ssl.PROTOCOL_TLSv1_2, False)
+        try_protocol_combo(ssl.PROTOCOL_TLSv1_2, ssl.PROTOCOL_TLSv1_1, False)
+        try_protocol_combo(ssl.PROTOCOL_TLSv1_1, ssl.PROTOCOL_TLSv1_2, False)
+
+    def test_starttls(self):
+        """Switching from clear text to encrypted and back again."""
+        msgs = (b"msg 1", b"MSG 2", b"STARTTLS", b"MSG 3", b"msg 4", b"ENDTLS", b"msg 5", b"msg 6")
+
+        server = ThreadedEchoServer(CERTFILE,
+                                    ssl_version=ssl.PROTOCOL_TLSv1,
+                                    starttls_server=True,
+                                    chatty=True,
+                                    connectionchatty=True)
+        wrapped = False
+        with server:
+            s = socket.socket()
+            s.setblocking(1)
+            s.connect((HOST, server.port))
             if support.verbose:
                 sys.stdout.write("\n")
-            if hasattr(ssl, 'PROTOCOL_SSLv2'):
-                try:
-                    try_protocol_combo(ssl.PROTOCOL_SSLv23, ssl.PROTOCOL_SSLv2, True)
-                except OSError as x:
-                    # this fails on some older versions of OpenSSL (0.9.7l, for instance)
+            for indata in msgs:
+                if support.verbose:
+                    sys.stdout.write(
+                        " client:  sending %r...\n" % indata)
+                if wrapped:
+                    conn.write(indata)
+                    outdata = conn.read()
+                else:
+                    s.send(indata)
+                    outdata = s.recv(1024)
+                msg = outdata.strip().lower()
+                if indata == b"STARTTLS" and msg.startswith(b"ok"):
+                    # STARTTLS ok, switch to secure mode
                     if support.verbose:
                         sys.stdout.write(
-                            " SSL2 client to SSL23 server test unexpectedly failed:\n %s\n"
-                            % str(x))
-            if hasattr(ssl, 'PROTOCOL_SSLv3'):
-                try_protocol_combo(ssl.PROTOCOL_SSLv23, ssl.PROTOCOL_SSLv3, False)
-            try_protocol_combo(ssl.PROTOCOL_SSLv23, ssl.PROTOCOL_SSLv23, True)
-            try_protocol_combo(ssl.PROTOCOL_SSLv23, ssl.PROTOCOL_TLSv1, 'TLSv1')
-
-            if hasattr(ssl, 'PROTOCOL_SSLv3'):
-                try_protocol_combo(ssl.PROTOCOL_SSLv23, ssl.PROTOCOL_SSLv3, False, ssl.CERT_OPTIONAL)
-            try_protocol_combo(ssl.PROTOCOL_SSLv23, ssl.PROTOCOL_SSLv23, True, ssl.CERT_OPTIONAL)
-            try_protocol_combo(ssl.PROTOCOL_SSLv23, ssl.PROTOCOL_TLSv1, 'TLSv1', ssl.CERT_OPTIONAL)
-
-            if hasattr(ssl, 'PROTOCOL_SSLv3'):
-                try_protocol_combo(ssl.PROTOCOL_SSLv23, ssl.PROTOCOL_SSLv3, False, ssl.CERT_REQUIRED)
-            try_protocol_combo(ssl.PROTOCOL_SSLv23, ssl.PROTOCOL_SSLv23, True, ssl.CERT_REQUIRED)
-            try_protocol_combo(ssl.PROTOCOL_SSLv23, ssl.PROTOCOL_TLSv1, 'TLSv1', ssl.CERT_REQUIRED)
-
-            # Server with specific SSL options
-            if hasattr(ssl, 'PROTOCOL_SSLv3'):
-                try_protocol_combo(ssl.PROTOCOL_SSLv23, ssl.PROTOCOL_SSLv3, False,
-                               server_options=ssl.OP_NO_SSLv3)
-            # Will choose TLSv1
-            try_protocol_combo(ssl.PROTOCOL_SSLv23, ssl.PROTOCOL_SSLv23, True,
-                               server_options=ssl.OP_NO_SSLv2 | ssl.OP_NO_SSLv3)
-            try_protocol_combo(ssl.PROTOCOL_SSLv23, ssl.PROTOCOL_TLSv1, False,
-                               server_options=ssl.OP_NO_TLSv1)
-
-
-        @skip_if_broken_ubuntu_ssl
-        @unittest.skipUnless(hasattr(ssl, 'PROTOCOL_SSLv3'),
-                             "OpenSSL is compiled without SSLv3 support")
-        def test_protocol_sslv3(self):
-            """Connecting to an SSLv3 server with various client options"""
-            if support.verbose:
-                sys.stdout.write("\n")
-            try_protocol_combo(ssl.PROTOCOL_SSLv3, ssl.PROTOCOL_SSLv3, 'SSLv3')
-            try_protocol_combo(ssl.PROTOCOL_SSLv3, ssl.PROTOCOL_SSLv3, 'SSLv3', ssl.CERT_OPTIONAL)
-            try_protocol_combo(ssl.PROTOCOL_SSLv3, ssl.PROTOCOL_SSLv3, 'SSLv3', ssl.CERT_REQUIRED)
-            if hasattr(ssl, 'PROTOCOL_SSLv2'):
-                try_protocol_combo(ssl.PROTOCOL_SSLv3, ssl.PROTOCOL_SSLv2, False)
-            try_protocol_combo(ssl.PROTOCOL_SSLv3, ssl.PROTOCOL_SSLv23, False,
-                               client_options=ssl.OP_NO_SSLv3)
-            try_protocol_combo(ssl.PROTOCOL_SSLv3, ssl.PROTOCOL_TLSv1, False)
-            if no_sslv2_implies_sslv3_hello():
-                # No SSLv2 => client will use an SSLv3 hello on recent OpenSSLs
-                try_protocol_combo(ssl.PROTOCOL_SSLv3, ssl.PROTOCOL_SSLv23,
-                                   False, client_options=ssl.OP_NO_SSLv2)
-
-        @skip_if_broken_ubuntu_ssl
-        def test_protocol_tlsv1(self):
-            """Connecting to a TLSv1 server with various client options"""
-            if support.verbose:
-                sys.stdout.write("\n")
-            try_protocol_combo(ssl.PROTOCOL_TLSv1, ssl.PROTOCOL_TLSv1, 'TLSv1')
-            try_protocol_combo(ssl.PROTOCOL_TLSv1, ssl.PROTOCOL_TLSv1, 'TLSv1', ssl.CERT_OPTIONAL)
-            try_protocol_combo(ssl.PROTOCOL_TLSv1, ssl.PROTOCOL_TLSv1, 'TLSv1', ssl.CERT_REQUIRED)
-            if hasattr(ssl, 'PROTOCOL_SSLv2'):
-                try_protocol_combo(ssl.PROTOCOL_TLSv1, ssl.PROTOCOL_SSLv2, False)
-            if hasattr(ssl, 'PROTOCOL_SSLv3'):
-                try_protocol_combo(ssl.PROTOCOL_TLSv1, ssl.PROTOCOL_SSLv3, False)
-            try_protocol_combo(ssl.PROTOCOL_TLSv1, ssl.PROTOCOL_SSLv23, False,
-                               client_options=ssl.OP_NO_TLSv1)
-
-        @skip_if_broken_ubuntu_ssl
-        @unittest.skipUnless(hasattr(ssl, "PROTOCOL_TLSv1_1"),
-                             "TLS version 1.1 not supported.")
-        def test_protocol_tlsv1_1(self):
-            """Connecting to a TLSv1.1 server with various client options.
-               Testing against older TLS versions."""
-            if support.verbose:
-                sys.stdout.write("\n")
-            try_protocol_combo(ssl.PROTOCOL_TLSv1_1, ssl.PROTOCOL_TLSv1_1, 'TLSv1.1')
-            if hasattr(ssl, 'PROTOCOL_SSLv2'):
-                try_protocol_combo(ssl.PROTOCOL_TLSv1_1, ssl.PROTOCOL_SSLv2, False)
-            if hasattr(ssl, 'PROTOCOL_SSLv3'):
-                try_protocol_combo(ssl.PROTOCOL_TLSv1_1, ssl.PROTOCOL_SSLv3, False)
-            try_protocol_combo(ssl.PROTOCOL_TLSv1_1, ssl.PROTOCOL_SSLv23, False,
-                               client_options=ssl.OP_NO_TLSv1_1)
-
-            try_protocol_combo(ssl.PROTOCOL_SSLv23, ssl.PROTOCOL_TLSv1_1, 'TLSv1.1')
-            try_protocol_combo(ssl.PROTOCOL_TLSv1_1, ssl.PROTOCOL_TLSv1, False)
-            try_protocol_combo(ssl.PROTOCOL_TLSv1, ssl.PROTOCOL_TLSv1_1, False)
-
-
-        @skip_if_broken_ubuntu_ssl
-        @unittest.skipUnless(hasattr(ssl, "PROTOCOL_TLSv1_2"),
-                             "TLS version 1.2 not supported.")
-        def test_protocol_tlsv1_2(self):
-            """Connecting to a TLSv1.2 server with various client options.
-               Testing against older TLS versions."""
-            if support.verbose:
-                sys.stdout.write("\n")
-            try_protocol_combo(ssl.PROTOCOL_TLSv1_2, ssl.PROTOCOL_TLSv1_2, 'TLSv1.2',
-                               server_options=ssl.OP_NO_SSLv3|ssl.OP_NO_SSLv2,
-                               client_options=ssl.OP_NO_SSLv3|ssl.OP_NO_SSLv2,)
-            if hasattr(ssl, 'PROTOCOL_SSLv2'):
-                try_protocol_combo(ssl.PROTOCOL_TLSv1_2, ssl.PROTOCOL_SSLv2, False)
-            if hasattr(ssl, 'PROTOCOL_SSLv3'):
-                try_protocol_combo(ssl.PROTOCOL_TLSv1_2, ssl.PROTOCOL_SSLv3, False)
-            try_protocol_combo(ssl.PROTOCOL_TLSv1_2, ssl.PROTOCOL_SSLv23, False,
-                               client_options=ssl.OP_NO_TLSv1_2)
-
-            try_protocol_combo(ssl.PROTOCOL_SSLv23, ssl.PROTOCOL_TLSv1_2, 'TLSv1.2')
-            try_protocol_combo(ssl.PROTOCOL_TLSv1_2, ssl.PROTOCOL_TLSv1, False)
-            try_protocol_combo(ssl.PROTOCOL_TLSv1, ssl.PROTOCOL_TLSv1_2, False)
-            try_protocol_combo(ssl.PROTOCOL_TLSv1_2, ssl.PROTOCOL_TLSv1_1, False)
-            try_protocol_combo(ssl.PROTOCOL_TLSv1_1, ssl.PROTOCOL_TLSv1_2, False)
-
-        def test_starttls(self):
-            """Switching from clear text to encrypted and back again."""
-            msgs = (b"msg 1", b"MSG 2", b"STARTTLS", b"MSG 3", b"msg 4", b"ENDTLS", b"msg 5", b"msg 6")
-
-            server = ThreadedEchoServer(CERTFILE,
-                                        ssl_version=ssl.PROTOCOL_TLSv1,
-                                        starttls_server=True,
-                                        chatty=True,
-                                        connectionchatty=True)
-            wrapped = False
-            with server:
-                s = socket.socket()
-                s.setblocking(1)
-                s.connect((HOST, server.port))
-                if support.verbose:
-                    sys.stdout.write("\n")
-                for indata in msgs:
+                            " client:  read %r from server, starting TLS...\n"
+                            % msg)
+                    conn = test_wrap_socket(s, ssl_version=ssl.PROTOCOL_TLSv1)
+                    wrapped = True
+                elif indata == b"ENDTLS" and msg.startswith(b"ok"):
+                    # ENDTLS ok, switch back to clear text
                     if support.verbose:
                         sys.stdout.write(
-                            " client:  sending %r...\n" % indata)
-                    if wrapped:
-                        conn.write(indata)
-                        outdata = conn.read()
-                    else:
-                        s.send(indata)
-                        outdata = s.recv(1024)
-                    msg = outdata.strip().lower()
-                    if indata == b"STARTTLS" and msg.startswith(b"ok"):
-                        # STARTTLS ok, switch to secure mode
-                        if support.verbose:
-                            sys.stdout.write(
-                                " client:  read %r from server, starting TLS...\n"
-                                % msg)
-                        conn = test_wrap_socket(s, ssl_version=ssl.PROTOCOL_TLSv1)
-                        wrapped = True
-                    elif indata == b"ENDTLS" and msg.startswith(b"ok"):
-                        # ENDTLS ok, switch back to clear text
-                        if support.verbose:
-                            sys.stdout.write(
-                                " client:  read %r from server, ending TLS...\n"
-                                % msg)
-                        s = conn.unwrap()
-                        wrapped = False
-                    else:
-                        if support.verbose:
-                            sys.stdout.write(
-                                " client:  read %r from server\n" % msg)
-                if support.verbose:
-                    sys.stdout.write(" client:  closing connection.\n")
-                if wrapped:
-                    conn.write(b"over\n")
+                            " client:  read %r from server, ending TLS...\n"
+                            % msg)
+                    s = conn.unwrap()
+                    wrapped = False
                 else:
-                    s.send(b"over\n")
-                if wrapped:
-                    conn.close()
-                else:
-                    s.close()
-
-        def test_socketserver(self):
-            """Using socketserver to create and manage SSL connections."""
-            server = make_https_server(self, certfile=CERTFILE)
-            # try to connect
-            if support.verbose:
-                sys.stdout.write('\n')
-            with open(CERTFILE, 'rb') as f:
-                d1 = f.read()
-            d2 = ''
-            # now fetch the same data from the HTTPS server
-            url = 'https://localhost:%d/%s' % (
-                server.port, os.path.split(CERTFILE)[1])
-            context = ssl.create_default_context(cafile=CERTFILE)
-            f = urllib.request.urlopen(url, context=context)
-            try:
-                dlen = f.info().get("content-length")
-                if dlen and (int(dlen) > 0):
-                    d2 = f.read(int(dlen))
                     if support.verbose:
                         sys.stdout.write(
-                            " client: read %d bytes from remote server '%s'\n"
-                            % (len(d2), server))
-            finally:
-                f.close()
-            self.assertEqual(d1, d2)
-
-        def test_asyncore_server(self):
-            """Check the example asyncore integration."""
+                            " client:  read %r from server\n" % msg)
             if support.verbose:
-                sys.stdout.write("\n")
+                sys.stdout.write(" client:  closing connection.\n")
+            if wrapped:
+                conn.write(b"over\n")
+            else:
+                s.send(b"over\n")
+            if wrapped:
+                conn.close()
+            else:
+                s.close()
 
-            indata = b"FOO\n"
-            server = AsyncoreEchoServer(CERTFILE)
-            with server:
-                s = test_wrap_socket(socket.socket())
-                s.connect(('127.0.0.1', server.port))
+    def test_socketserver(self):
+        """Using socketserver to create and manage SSL connections."""
+        server = make_https_server(self, certfile=CERTFILE)
+        # try to connect
+        if support.verbose:
+            sys.stdout.write('\n')
+        with open(CERTFILE, 'rb') as f:
+            d1 = f.read()
+        d2 = ''
+        # now fetch the same data from the HTTPS server
+        url = 'https://localhost:%d/%s' % (
+            server.port, os.path.split(CERTFILE)[1])
+        context = ssl.create_default_context(cafile=CERTFILE)
+        f = urllib.request.urlopen(url, context=context)
+        try:
+            dlen = f.info().get("content-length")
+            if dlen and (int(dlen) > 0):
+                d2 = f.read(int(dlen))
                 if support.verbose:
                     sys.stdout.write(
-                        " client:  sending %r...\n" % indata)
-                s.write(indata)
-                outdata = s.read()
-                if support.verbose:
-                    sys.stdout.write(" client:  read %r\n" % outdata)
-                if outdata != indata.lower():
-                    self.fail(
-                        "bad data <<%r>> (%d) received; expected <<%r>> (%d)\n"
-                        % (outdata[:20], len(outdata),
-                           indata[:20].lower(), len(indata)))
-                s.write(b"over\n")
-                if support.verbose:
-                    sys.stdout.write(" client:  closing connection.\n")
-                s.close()
-                if support.verbose:
-                    sys.stdout.write(" client:  connection closed.\n")
+                        " client: read %d bytes from remote server '%s'\n"
+                        % (len(d2), server))
+        finally:
+            f.close()
+        self.assertEqual(d1, d2)
 
-        def test_recv_send(self):
-            """Test recv(), send() and friends."""
+    def test_asyncore_server(self):
+        """Check the example asyncore integration."""
+        if support.verbose:
+            sys.stdout.write("\n")
+
+        indata = b"FOO\n"
+        server = AsyncoreEchoServer(CERTFILE)
+        with server:
+            s = test_wrap_socket(socket.socket())
+            s.connect(('127.0.0.1', server.port))
             if support.verbose:
-                sys.stdout.write("\n")
+                sys.stdout.write(
+                    " client:  sending %r...\n" % indata)
+            s.write(indata)
+            outdata = s.read()
+            if support.verbose:
+                sys.stdout.write(" client:  read %r\n" % outdata)
+            if outdata != indata.lower():
+                self.fail(
+                    "bad data <<%r>> (%d) received; expected <<%r>> (%d)\n"
+                    % (outdata[:20], len(outdata),
+                       indata[:20].lower(), len(indata)))
+            s.write(b"over\n")
+            if support.verbose:
+                sys.stdout.write(" client:  closing connection.\n")
+            s.close()
+            if support.verbose:
+                sys.stdout.write(" client:  connection closed.\n")
 
-            server = ThreadedEchoServer(CERTFILE,
-                                        certreqs=ssl.CERT_NONE,
-                                        ssl_version=ssl.PROTOCOL_TLSv1,
-                                        cacerts=CERTFILE,
-                                        chatty=True,
-                                        connectionchatty=False)
-            with server:
-                s = test_wrap_socket(socket.socket(),
-                                    server_side=False,
-                                    certfile=CERTFILE,
-                                    ca_certs=CERTFILE,
-                                    cert_reqs=ssl.CERT_NONE,
-                                    ssl_version=ssl.PROTOCOL_TLSv1)
-                s.connect((HOST, server.port))
-                # helper methods for standardising recv* method signatures
-                def _recv_into():
-                    b = bytearray(b"\0"*100)
-                    count = s.recv_into(b)
-                    return b[:count]
-
-                def _recvfrom_into():
-                    b = bytearray(b"\0"*100)
-                    count, addr = s.recvfrom_into(b)
-                    return b[:count]
-
-                # (name, method, expect success?, *args, return value func)
-                send_methods = [
-                    ('send', s.send, True, [], len),
-                    ('sendto', s.sendto, False, ["some.address"], len),
-                    ('sendall', s.sendall, True, [], lambda x: None),
-                ]
-                # (name, method, whether to expect success, *args)
-                recv_methods = [
-                    ('recv', s.recv, True, []),
-                    ('recvfrom', s.recvfrom, False, ["some.address"]),
-                    ('recv_into', _recv_into, True, []),
-                    ('recvfrom_into', _recvfrom_into, False, []),
-                ]
-                data_prefix = "PREFIX_"
-
-                for (meth_name, send_meth, expect_success, args,
-                        ret_val_meth) in send_methods:
-                    indata = (data_prefix + meth_name).encode('ascii')
-                    try:
-                        ret = send_meth(indata, *args)
-                        msg = "sending with {}".format(meth_name)
-                        self.assertEqual(ret, ret_val_meth(indata), msg=msg)
-                        outdata = s.read()
-                        if outdata != indata.lower():
-                            self.fail(
-                                "While sending with <<{name:s}>> bad data "
-                                "<<{outdata:r}>> ({nout:d}) received; "
-                                "expected <<{indata:r}>> ({nin:d})\n".format(
-                                    name=meth_name, outdata=outdata[:20],
-                                    nout=len(outdata),
-                                    indata=indata[:20], nin=len(indata)
-                                )
-                            )
-                    except ValueError as e:
-                        if expect_success:
-                            self.fail(
-                                "Failed to send with method <<{name:s}>>; "
-                                "expected to succeed.\n".format(name=meth_name)
+    def test_recv_send(self):
+        """Test recv(), send() and friends."""
+        if support.verbose:
+            sys.stdout.write("\n")
+
+        server = ThreadedEchoServer(CERTFILE,
+                                    certreqs=ssl.CERT_NONE,
+                                    ssl_version=ssl.PROTOCOL_TLSv1,
+                                    cacerts=CERTFILE,
+                                    chatty=True,
+                                    connectionchatty=False)
+        with server:
+            s = test_wrap_socket(socket.socket(),
+                                server_side=False,
+                                certfile=CERTFILE,
+                                ca_certs=CERTFILE,
+                                cert_reqs=ssl.CERT_NONE,
+                                ssl_version=ssl.PROTOCOL_TLSv1)
+            s.connect((HOST, server.port))
+            # helper methods for standardising recv* method signatures
+            def _recv_into():
+                b = bytearray(b"\0"*100)
+                count = s.recv_into(b)
+                return b[:count]
+
+            def _recvfrom_into():
+                b = bytearray(b"\0"*100)
+                count, addr = s.recvfrom_into(b)
+                return b[:count]
+
+            # (name, method, expect success?, *args, return value func)
+            send_methods = [
+                ('send', s.send, True, [], len),
+                ('sendto', s.sendto, False, ["some.address"], len),
+                ('sendall', s.sendall, True, [], lambda x: None),
+            ]
+            # (name, method, whether to expect success, *args)
+            recv_methods = [
+                ('recv', s.recv, True, []),
+                ('recvfrom', s.recvfrom, False, ["some.address"]),
+                ('recv_into', _recv_into, True, []),
+                ('recvfrom_into', _recvfrom_into, False, []),
+            ]
+            data_prefix = "PREFIX_"
+
+            for (meth_name, send_meth, expect_success, args,
+                    ret_val_meth) in send_methods:
+                indata = (data_prefix + meth_name).encode('ascii')
+                try:
+                    ret = send_meth(indata, *args)
+                    msg = "sending with {}".format(meth_name)
+                    self.assertEqual(ret, ret_val_meth(indata), msg=msg)
+                    outdata = s.read()
+                    if outdata != indata.lower():
+                        self.fail(
+                            "While sending with <<{name:s}>> bad data "
+                            "<<{outdata:r}>> ({nout:d}) received; "
+                            "expected <<{indata:r}>> ({nin:d})\n".format(
+                                name=meth_name, outdata=outdata[:20],
+                                nout=len(outdata),
+                                indata=indata[:20], nin=len(indata)
                             )
-                        if not str(e).startswith(meth_name):
-                            self.fail(
-                                "Method <<{name:s}>> failed with unexpected "
-                                "exception message: {exp:s}\n".format(
-                                    name=meth_name, exp=e
-                                )
+                        )
+                except ValueError as e:
+                    if expect_success:
+                        self.fail(
+                            "Failed to send with method <<{name:s}>>; "
+                            "expected to succeed.\n".format(name=meth_name)
+                        )
+                    if not str(e).startswith(meth_name):
+                        self.fail(
+                            "Method <<{name:s}>> failed with unexpected "
+                            "exception message: {exp:s}\n".format(
+                                name=meth_name, exp=e
                             )
+                        )
 
-                for meth_name, recv_meth, expect_success, args in recv_methods:
-                    indata = (data_prefix + meth_name).encode('ascii')
-                    try:
-                        s.send(indata)
-                        outdata = recv_meth(*args)
-                        if outdata != indata.lower():
-                            self.fail(
-                                "While receiving with <<{name:s}>> bad data "
-                                "<<{outdata:r}>> ({nout:d}) received; "
-                                "expected <<{indata:r}>> ({nin:d})\n".format(
-                                    name=meth_name, outdata=outdata[:20],
-                                    nout=len(outdata),
-                                    indata=indata[:20], nin=len(indata)
-                                )
-                            )
-                    except ValueError as e:
-                        if expect_success:
-                            self.fail(
-                                "Failed to receive with method <<{name:s}>>; "
-                                "expected to succeed.\n".format(name=meth_name)
+            for meth_name, recv_meth, expect_success, args in recv_methods:
+                indata = (data_prefix + meth_name).encode('ascii')
+                try:
+                    s.send(indata)
+                    outdata = recv_meth(*args)
+                    if outdata != indata.lower():
+                        self.fail(
+                            "While receiving with <<{name:s}>> bad data "
+                            "<<{outdata:r}>> ({nout:d}) received; "
+                            "expected <<{indata:r}>> ({nin:d})\n".format(
+                                name=meth_name, outdata=outdata[:20],
+                                nout=len(outdata),
+                                indata=indata[:20], nin=len(indata)
                             )
-                        if not str(e).startswith(meth_name):
-                            self.fail(
-                                "Method <<{name:s}>> failed with unexpected "
-                                "exception message: {exp:s}\n".format(
-                                    name=meth_name, exp=e
-                                )
+                        )
+                except ValueError as e:
+                    if expect_success:
+                        self.fail(
+                            "Failed to receive with method <<{name:s}>>; "
+                            "expected to succeed.\n".format(name=meth_name)
+                        )
+                    if not str(e).startswith(meth_name):
+                        self.fail(
+                            "Method <<{name:s}>> failed with unexpected "
+                            "exception message: {exp:s}\n".format(
+                                name=meth_name, exp=e
                             )
-                        # consume data
-                        s.read()
+                        )
+                    # consume data
+                    s.read()
 
-                # read(-1, buffer) is supported, even though read(-1) is not
-                data = b"data"
-                s.send(data)
-                buffer = bytearray(len(data))
-                self.assertEqual(s.read(-1, buffer), len(data))
-                self.assertEqual(buffer, data)
+            # read(-1, buffer) is supported, even though read(-1) is not
+            data = b"data"
+            s.send(data)
+            buffer = bytearray(len(data))
+            self.assertEqual(s.read(-1, buffer), len(data))
+            self.assertEqual(buffer, data)
 
-                # Make sure sendmsg et al are disallowed to avoid
-                # inadvertent disclosure of data and/or corruption
-                # of the encrypted data stream
-                self.assertRaises(NotImplementedError, s.sendmsg, [b"data"])
-                self.assertRaises(NotImplementedError, s.recvmsg, 100)
-                self.assertRaises(NotImplementedError,
-                                  s.recvmsg_into, bytearray(100))
+            # Make sure sendmsg et al are disallowed to avoid
+            # inadvertent disclosure of data and/or corruption
+            # of the encrypted data stream
+            self.assertRaises(NotImplementedError, s.sendmsg, [b"data"])
+            self.assertRaises(NotImplementedError, s.recvmsg, 100)
+            self.assertRaises(NotImplementedError,
+                              s.recvmsg_into, bytearray(100))
 
-                s.write(b"over\n")
+            s.write(b"over\n")
 
-                self.assertRaises(ValueError, s.recv, -1)
-                self.assertRaises(ValueError, s.read, -1)
+            self.assertRaises(ValueError, s.recv, -1)
+            self.assertRaises(ValueError, s.read, -1)
 
-                s.close()
+            s.close()
 
-        def test_recv_zero(self):
-            server = ThreadedEchoServer(CERTFILE)
-            server.__enter__()
-            self.addCleanup(server.__exit__, None, None)
-            s = socket.create_connection((HOST, server.port))
-            self.addCleanup(s.close)
-            s = test_wrap_socket(s, suppress_ragged_eofs=False)
-            self.addCleanup(s.close)
+    def test_recv_zero(self):
+        server = ThreadedEchoServer(CERTFILE)
+        server.__enter__()
+        self.addCleanup(server.__exit__, None, None)
+        s = socket.create_connection((HOST, server.port))
+        self.addCleanup(s.close)
+        s = test_wrap_socket(s, suppress_ragged_eofs=False)
+        self.addCleanup(s.close)
 
-            # recv/read(0) should return no data
-            s.send(b"data")
-            self.assertEqual(s.recv(0), b"")
-            self.assertEqual(s.read(0), b"")
-            self.assertEqual(s.read(), b"data")
+        # recv/read(0) should return no data
+        s.send(b"data")
+        self.assertEqual(s.recv(0), b"")
+        self.assertEqual(s.read(0), b"")
+        self.assertEqual(s.read(), b"data")
+
+        # Should not block if the other end sends no data
+        s.setblocking(False)
+        self.assertEqual(s.recv(0), b"")
+        self.assertEqual(s.recv_into(bytearray()), 0)
 
-            # Should not block if the other end sends no data
+    def test_nonblocking_send(self):
+        server = ThreadedEchoServer(CERTFILE,
+                                    certreqs=ssl.CERT_NONE,
+                                    ssl_version=ssl.PROTOCOL_TLSv1,
+                                    cacerts=CERTFILE,
+                                    chatty=True,
+                                    connectionchatty=False)
+        with server:
+            s = test_wrap_socket(socket.socket(),
+                                server_side=False,
+                                certfile=CERTFILE,
+                                ca_certs=CERTFILE,
+                                cert_reqs=ssl.CERT_NONE,
+                                ssl_version=ssl.PROTOCOL_TLSv1)
+            s.connect((HOST, server.port))
             s.setblocking(False)
-            self.assertEqual(s.recv(0), b"")
-            self.assertEqual(s.recv_into(bytearray()), 0)
-
-        def test_nonblocking_send(self):
-            server = ThreadedEchoServer(CERTFILE,
-                                        certreqs=ssl.CERT_NONE,
-                                        ssl_version=ssl.PROTOCOL_TLSv1,
-                                        cacerts=CERTFILE,
-                                        chatty=True,
-                                        connectionchatty=False)
-            with server:
-                s = test_wrap_socket(socket.socket(),
-                                    server_side=False,
-                                    certfile=CERTFILE,
-                                    ca_certs=CERTFILE,
-                                    cert_reqs=ssl.CERT_NONE,
-                                    ssl_version=ssl.PROTOCOL_TLSv1)
-                s.connect((HOST, server.port))
-                s.setblocking(False)
-
-                # If we keep sending data, at some point the buffers
-                # will be full and the call will block
-                buf = bytearray(8192)
-                def fill_buffer():
-                    while True:
-                        s.send(buf)
-                self.assertRaises((ssl.SSLWantWriteError,
-                                   ssl.SSLWantReadError), fill_buffer)
-
-                # Now read all the output and discard it
-                s.setblocking(True)
-                s.close()
 
-        def test_handshake_timeout(self):
-            # Issue #5103: SSL handshake must respect the socket timeout
-            server = socket.socket(socket.AF_INET)
-            host = "127.0.0.1"
-            port = support.bind_port(server)
-            started = threading.Event()
-            finish = False
-
-            def serve():
-                server.listen()
-                started.set()
-                conns = []
-                while not finish:
-                    r, w, e = select.select([server], [], [], 0.1)
-                    if server in r:
-                        # Let the socket hang around rather than having
-                        # it closed by garbage collection.
-                        conns.append(server.accept()[0])
-                for sock in conns:
-                    sock.close()
-
-            t = threading.Thread(target=serve)
-            t.start()
-            started.wait()
+            # If we keep sending data, at some point the buffers
+            # will be full and the call will block
+            buf = bytearray(8192)
+            def fill_buffer():
+                while True:
+                    s.send(buf)
+            self.assertRaises((ssl.SSLWantWriteError,
+                               ssl.SSLWantReadError), fill_buffer)
+
+            # Now read all the output and discard it
+            s.setblocking(True)
+            s.close()
+
+    def test_handshake_timeout(self):
+        # Issue #5103: SSL handshake must respect the socket timeout
+        server = socket.socket(socket.AF_INET)
+        host = "127.0.0.1"
+        port = support.bind_port(server)
+        started = threading.Event()
+        finish = False
+
+        def serve():
+            server.listen()
+            started.set()
+            conns = []
+            while not finish:
+                r, w, e = select.select([server], [], [], 0.1)
+                if server in r:
+                    # Let the socket hang around rather than having
+                    # it closed by garbage collection.
+                    conns.append(server.accept()[0])
+            for sock in conns:
+                sock.close()
+
+        t = threading.Thread(target=serve)
+        t.start()
+        started.wait()
 
+        try:
             try:
-                try:
-                    c = socket.socket(socket.AF_INET)
-                    c.settimeout(0.2)
-                    c.connect((host, port))
-                    # Will attempt handshake and time out
-                    self.assertRaisesRegex(socket.timeout, "timed out",
-                                           test_wrap_socket, c)
-                finally:
-                    c.close()
-                try:
-                    c = socket.socket(socket.AF_INET)
-                    c = test_wrap_socket(c)
-                    c.settimeout(0.2)
-                    # Will attempt handshake and time out
-                    self.assertRaisesRegex(socket.timeout, "timed out",
-                                           c.connect, (host, port))
-                finally:
-                    c.close()
+                c = socket.socket(socket.AF_INET)
+                c.settimeout(0.2)
+                c.connect((host, port))
+                # Will attempt handshake and time out
+                self.assertRaisesRegex(socket.timeout, "timed out",
+                                       test_wrap_socket, c)
             finally:
-                finish = True
-                t.join()
-                server.close()
-
-        def test_server_accept(self):
-            # Issue #16357: accept() on a SSLSocket created through
-            # SSLContext.wrap_socket().
-            context = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
-            context.verify_mode = ssl.CERT_REQUIRED
-            context.load_verify_locations(CERTFILE)
-            context.load_cert_chain(CERTFILE)
-            server = socket.socket(socket.AF_INET)
-            host = "127.0.0.1"
-            port = support.bind_port(server)
-            server = context.wrap_socket(server, server_side=True)
-            self.assertTrue(server.server_side)
-
-            evt = threading.Event()
-            remote = None
-            peer = None
-            def serve():
-                nonlocal remote, peer
-                server.listen()
-                # Block on the accept and wait on the connection to close.
-                evt.set()
-                remote, peer = server.accept()
-                remote.recv(1)
-
-            t = threading.Thread(target=serve)
-            t.start()
-            # Client wait until server setup and perform a connect.
-            evt.wait()
-            client = context.wrap_socket(socket.socket())
-            client.connect((host, port))
-            client_addr = client.getsockname()
-            client.close()
+                c.close()
+            try:
+                c = socket.socket(socket.AF_INET)
+                c = test_wrap_socket(c)
+                c.settimeout(0.2)
+                # Will attempt handshake and time out
+                self.assertRaisesRegex(socket.timeout, "timed out",
+                                       c.connect, (host, port))
+            finally:
+                c.close()
+        finally:
+            finish = True
             t.join()
-            remote.close()
             server.close()
-            # Sanity checks.
-            self.assertIsInstance(remote, ssl.SSLSocket)
-            self.assertEqual(peer, client_addr)
-
-        def test_getpeercert_enotconn(self):
-            context = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
-            with context.wrap_socket(socket.socket()) as sock:
-                with self.assertRaises(OSError) as cm:
-                    sock.getpeercert()
-                self.assertEqual(cm.exception.errno, errno.ENOTCONN)
-
-        def test_do_handshake_enotconn(self):
-            context = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
-            with context.wrap_socket(socket.socket()) as sock:
-                with self.assertRaises(OSError) as cm:
-                    sock.do_handshake()
-                self.assertEqual(cm.exception.errno, errno.ENOTCONN)
-
-        def test_default_ciphers(self):
-            context = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
-            try:
-                # Force a set of weak ciphers on our client context
-                context.set_ciphers("DES")
-            except ssl.SSLError:
-                self.skipTest("no DES cipher available")
-            with ThreadedEchoServer(CERTFILE,
-                                    ssl_version=ssl.PROTOCOL_SSLv23,
-                                    chatty=False) as server:
-                with context.wrap_socket(socket.socket()) as s:
-                    with self.assertRaises(OSError):
-                        s.connect((HOST, server.port))
-            self.assertIn("no shared cipher", server.conn_errors[0])
-
-        def test_version_basic(self):
-            """
-            Basic tests for SSLSocket.version().
-            More tests are done in the test_protocol_*() methods.
-            """
-            context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
-            with ThreadedEchoServer(CERTFILE,
-                                    ssl_version=ssl.PROTOCOL_TLSv1,
-                                    chatty=False) as server:
-                with context.wrap_socket(socket.socket()) as s:
-                    self.assertIs(s.version(), None)
-                    s.connect((HOST, server.port))
-                    self.assertEqual(s.version(), 'TLSv1')
-                self.assertIs(s.version(), None)
 
-        @unittest.skipUnless(ssl.HAS_ECDH, "test requires ECDH-enabled OpenSSL")
-        def test_default_ecdh_curve(self):
-            # Issue #21015: elliptic curve-based Diffie Hellman key exchange
-            # should be enabled by default on SSL contexts.
-            context = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
-            context.load_cert_chain(CERTFILE)
-            # Prior to OpenSSL 1.0.0, ECDH ciphers have to be enabled
-            # explicitly using the 'ECCdraft' cipher alias.  Otherwise,
-            # our default cipher list should prefer ECDH-based ciphers
-            # automatically.
-            if ssl.OPENSSL_VERSION_INFO < (1, 0, 0):
-                context.set_ciphers("ECCdraft:ECDH")
-            with ThreadedEchoServer(context=context) as server:
-                with context.wrap_socket(socket.socket()) as s:
+    def test_server_accept(self):
+        # Issue #16357: accept() on a SSLSocket created through
+        # SSLContext.wrap_socket().
+        context = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
+        context.verify_mode = ssl.CERT_REQUIRED
+        context.load_verify_locations(CERTFILE)
+        context.load_cert_chain(CERTFILE)
+        server = socket.socket(socket.AF_INET)
+        host = "127.0.0.1"
+        port = support.bind_port(server)
+        server = context.wrap_socket(server, server_side=True)
+        self.assertTrue(server.server_side)
+
+        evt = threading.Event()
+        remote = None
+        peer = None
+        def serve():
+            nonlocal remote, peer
+            server.listen()
+            # Block on the accept and wait on the connection to close.
+            evt.set()
+            remote, peer = server.accept()
+            remote.recv(1)
+
+        t = threading.Thread(target=serve)
+        t.start()
+        # Client wait until server setup and perform a connect.
+        evt.wait()
+        client = context.wrap_socket(socket.socket())
+        client.connect((host, port))
+        client_addr = client.getsockname()
+        client.close()
+        t.join()
+        remote.close()
+        server.close()
+        # Sanity checks.
+        self.assertIsInstance(remote, ssl.SSLSocket)
+        self.assertEqual(peer, client_addr)
+
+    def test_getpeercert_enotconn(self):
+        context = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
+        with context.wrap_socket(socket.socket()) as sock:
+            with self.assertRaises(OSError) as cm:
+                sock.getpeercert()
+            self.assertEqual(cm.exception.errno, errno.ENOTCONN)
+
+    def test_do_handshake_enotconn(self):
+        context = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
+        with context.wrap_socket(socket.socket()) as sock:
+            with self.assertRaises(OSError) as cm:
+                sock.do_handshake()
+            self.assertEqual(cm.exception.errno, errno.ENOTCONN)
+
+    def test_default_ciphers(self):
+        context = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
+        try:
+            # Force a set of weak ciphers on our client context
+            context.set_ciphers("DES")
+        except ssl.SSLError:
+            self.skipTest("no DES cipher available")
+        with ThreadedEchoServer(CERTFILE,
+                                ssl_version=ssl.PROTOCOL_SSLv23,
+                                chatty=False) as server:
+            with context.wrap_socket(socket.socket()) as s:
+                with self.assertRaises(OSError):
                     s.connect((HOST, server.port))
-                    self.assertIn("ECDH", s.cipher()[0])
+        self.assertIn("no shared cipher", server.conn_errors[0])
 
-        @unittest.skipUnless("tls-unique" in ssl.CHANNEL_BINDING_TYPES,
-                             "'tls-unique' channel binding not available")
-        def test_tls_unique_channel_binding(self):
-            """Test tls-unique channel binding."""
-            if support.verbose:
-                sys.stdout.write("\n")
-
-            server = ThreadedEchoServer(CERTFILE,
-                                        certreqs=ssl.CERT_NONE,
-                                        ssl_version=ssl.PROTOCOL_TLSv1,
-                                        cacerts=CERTFILE,
-                                        chatty=True,
-                                        connectionchatty=False)
-            with server:
-                s = test_wrap_socket(socket.socket(),
-                                    server_side=False,
-                                    certfile=CERTFILE,
-                                    ca_certs=CERTFILE,
-                                    cert_reqs=ssl.CERT_NONE,
-                                    ssl_version=ssl.PROTOCOL_TLSv1)
+    def test_version_basic(self):
+        """
+        Basic tests for SSLSocket.version().
+        More tests are done in the test_protocol_*() methods.
+        """
+        context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
+        with ThreadedEchoServer(CERTFILE,
+                                ssl_version=ssl.PROTOCOL_TLSv1,
+                                chatty=False) as server:
+            with context.wrap_socket(socket.socket()) as s:
+                self.assertIs(s.version(), None)
                 s.connect((HOST, server.port))
-                # get the data
-                cb_data = s.get_channel_binding("tls-unique")
-                if support.verbose:
-                    sys.stdout.write(" got channel binding data: {0!r}\n"
-                                     .format(cb_data))
-
-                # check if it is sane
-                self.assertIsNotNone(cb_data)
-                self.assertEqual(len(cb_data), 12) # True for TLSv1
-
-                # and compare with the peers version
-                s.write(b"CB tls-unique\n")
-                peer_data_repr = s.read().strip()
-                self.assertEqual(peer_data_repr,
-                                 repr(cb_data).encode("us-ascii"))
-                s.close()
-
-                # now, again
-                s = test_wrap_socket(socket.socket(),
-                                    server_side=False,
-                                    certfile=CERTFILE,
-                                    ca_certs=CERTFILE,
-                                    cert_reqs=ssl.CERT_NONE,
-                                    ssl_version=ssl.PROTOCOL_TLSv1)
+                self.assertEqual(s.version(), 'TLSv1')
+            self.assertIs(s.version(), None)
+
+    @unittest.skipUnless(ssl.HAS_ECDH, "test requires ECDH-enabled OpenSSL")
+    def test_default_ecdh_curve(self):
+        # Issue #21015: elliptic curve-based Diffie Hellman key exchange
+        # should be enabled by default on SSL contexts.
+        context = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
+        context.load_cert_chain(CERTFILE)
+        # Prior to OpenSSL 1.0.0, ECDH ciphers have to be enabled
+        # explicitly using the 'ECCdraft' cipher alias.  Otherwise,
+        # our default cipher list should prefer ECDH-based ciphers
+        # automatically.
+        if ssl.OPENSSL_VERSION_INFO < (1, 0, 0):
+            context.set_ciphers("ECCdraft:ECDH")
+        with ThreadedEchoServer(context=context) as server:
+            with context.wrap_socket(socket.socket()) as s:
                 s.connect((HOST, server.port))
-                new_cb_data = s.get_channel_binding("tls-unique")
-                if support.verbose:
-                    sys.stdout.write(" got another channel binding data: {0!r}\n"
-                                     .format(new_cb_data))
-                # is it really unique
-                self.assertNotEqual(cb_data, new_cb_data)
-                self.assertIsNotNone(cb_data)
-                self.assertEqual(len(cb_data), 12) # True for TLSv1
-                s.write(b"CB tls-unique\n")
-                peer_data_repr = s.read().strip()
-                self.assertEqual(peer_data_repr,
-                                 repr(new_cb_data).encode("us-ascii"))
-                s.close()
+                self.assertIn("ECDH", s.cipher()[0])
 
-        def test_compression(self):
-            context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
-            context.load_cert_chain(CERTFILE)
-            stats = server_params_test(context, context,
-                                       chatty=True, connectionchatty=True)
-            if support.verbose:
-                sys.stdout.write(" got compression: {!r}\n".format(stats['compression']))
-            self.assertIn(stats['compression'], { None, 'ZLIB', 'RLE' })
-
-        @unittest.skipUnless(hasattr(ssl, 'OP_NO_COMPRESSION'),
-                             "ssl.OP_NO_COMPRESSION needed for this test")
-        def test_compression_disabled(self):
-            context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
-            context.load_cert_chain(CERTFILE)
-            context.options |= ssl.OP_NO_COMPRESSION
-            stats = server_params_test(context, context,
-                                       chatty=True, connectionchatty=True)
-            self.assertIs(stats['compression'], None)
-
-        def test_dh_params(self):
-            # Check we can get a connection with ephemeral Diffie-Hellman
-            context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
-            context.load_cert_chain(CERTFILE)
-            context.load_dh_params(DHFILE)
-            context.set_ciphers("kEDH")
-            stats = server_params_test(context, context,
-                                       chatty=True, connectionchatty=True)
-            cipher = stats["cipher"][0]
-            parts = cipher.split("-")
-            if "ADH" not in parts and "EDH" not in parts and "DHE" not in parts:
-                self.fail("Non-DH cipher: " + cipher[0])
-
-        def test_selected_alpn_protocol(self):
-            # selected_alpn_protocol() is None unless ALPN is used.
-            context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
-            context.load_cert_chain(CERTFILE)
-            stats = server_params_test(context, context,
-                                       chatty=True, connectionchatty=True)
-            self.assertIs(stats['client_alpn_protocol'], None)
+    @unittest.skipUnless("tls-unique" in ssl.CHANNEL_BINDING_TYPES,
+                         "'tls-unique' channel binding not available")
+    def test_tls_unique_channel_binding(self):
+        """Test tls-unique channel binding."""
+        if support.verbose:
+            sys.stdout.write("\n")
 
-        @unittest.skipUnless(ssl.HAS_ALPN, "ALPN support required")
-        def test_selected_alpn_protocol_if_server_uses_alpn(self):
-            # selected_alpn_protocol() is None unless ALPN is used by the client.
-            client_context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
-            client_context.load_verify_locations(CERTFILE)
-            server_context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
+        server = ThreadedEchoServer(CERTFILE,
+                                    certreqs=ssl.CERT_NONE,
+                                    ssl_version=ssl.PROTOCOL_TLSv1,
+                                    cacerts=CERTFILE,
+                                    chatty=True,
+                                    connectionchatty=False)
+        with server:
+            s = test_wrap_socket(socket.socket(),
+                                server_side=False,
+                                certfile=CERTFILE,
+                                ca_certs=CERTFILE,
+                                cert_reqs=ssl.CERT_NONE,
+                                ssl_version=ssl.PROTOCOL_TLSv1)
+            s.connect((HOST, server.port))
+            # get the data
+            cb_data = s.get_channel_binding("tls-unique")
+            if support.verbose:
+                sys.stdout.write(" got channel binding data: {0!r}\n"
+                                 .format(cb_data))
+
+            # check if it is sane
+            self.assertIsNotNone(cb_data)
+            self.assertEqual(len(cb_data), 12) # True for TLSv1
+
+            # and compare with the peers version
+            s.write(b"CB tls-unique\n")
+            peer_data_repr = s.read().strip()
+            self.assertEqual(peer_data_repr,
+                             repr(cb_data).encode("us-ascii"))
+            s.close()
+
+            # now, again
+            s = test_wrap_socket(socket.socket(),
+                                server_side=False,
+                                certfile=CERTFILE,
+                                ca_certs=CERTFILE,
+                                cert_reqs=ssl.CERT_NONE,
+                                ssl_version=ssl.PROTOCOL_TLSv1)
+            s.connect((HOST, server.port))
+            new_cb_data = s.get_channel_binding("tls-unique")
+            if support.verbose:
+                sys.stdout.write(" got another channel binding data: {0!r}\n"
+                                 .format(new_cb_data))
+            # is it really unique
+            self.assertNotEqual(cb_data, new_cb_data)
+            self.assertIsNotNone(cb_data)
+            self.assertEqual(len(cb_data), 12) # True for TLSv1
+            s.write(b"CB tls-unique\n")
+            peer_data_repr = s.read().strip()
+            self.assertEqual(peer_data_repr,
+                             repr(new_cb_data).encode("us-ascii"))
+            s.close()
+
+    def test_compression(self):
+        context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
+        context.load_cert_chain(CERTFILE)
+        stats = server_params_test(context, context,
+                                   chatty=True, connectionchatty=True)
+        if support.verbose:
+            sys.stdout.write(" got compression: {!r}\n".format(stats['compression']))
+        self.assertIn(stats['compression'], { None, 'ZLIB', 'RLE' })
+
+    @unittest.skipUnless(hasattr(ssl, 'OP_NO_COMPRESSION'),
+                         "ssl.OP_NO_COMPRESSION needed for this test")
+    def test_compression_disabled(self):
+        context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
+        context.load_cert_chain(CERTFILE)
+        context.options |= ssl.OP_NO_COMPRESSION
+        stats = server_params_test(context, context,
+                                   chatty=True, connectionchatty=True)
+        self.assertIs(stats['compression'], None)
+
+    def test_dh_params(self):
+        # Check we can get a connection with ephemeral Diffie-Hellman
+        context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
+        context.load_cert_chain(CERTFILE)
+        context.load_dh_params(DHFILE)
+        context.set_ciphers("kEDH")
+        stats = server_params_test(context, context,
+                                   chatty=True, connectionchatty=True)
+        cipher = stats["cipher"][0]
+        parts = cipher.split("-")
+        if "ADH" not in parts and "EDH" not in parts and "DHE" not in parts:
+            self.fail("Non-DH cipher: " + cipher[0])
+
+    def test_selected_alpn_protocol(self):
+        # selected_alpn_protocol() is None unless ALPN is used.
+        context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
+        context.load_cert_chain(CERTFILE)
+        stats = server_params_test(context, context,
+                                   chatty=True, connectionchatty=True)
+        self.assertIs(stats['client_alpn_protocol'], None)
+
+    @unittest.skipUnless(ssl.HAS_ALPN, "ALPN support required")
+    def test_selected_alpn_protocol_if_server_uses_alpn(self):
+        # selected_alpn_protocol() is None unless ALPN is used by the client.
+        client_context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
+        client_context.load_verify_locations(CERTFILE)
+        server_context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
+        server_context.load_cert_chain(CERTFILE)
+        server_context.set_alpn_protocols(['foo', 'bar'])
+        stats = server_params_test(client_context, server_context,
+                                   chatty=True, connectionchatty=True)
+        self.assertIs(stats['client_alpn_protocol'], None)
+
+    @unittest.skipUnless(ssl.HAS_ALPN, "ALPN support needed for this test")
+    def test_alpn_protocols(self):
+        server_protocols = ['foo', 'bar', 'milkshake']
+        protocol_tests = [
+            (['foo', 'bar'], 'foo'),
+            (['bar', 'foo'], 'foo'),
+            (['milkshake'], 'milkshake'),
+            (['http/3.0', 'http/4.0'], None)
+        ]
+        for client_protocols, expected in protocol_tests:
+            server_context = ssl.SSLContext(ssl.PROTOCOL_TLSv1_2)
             server_context.load_cert_chain(CERTFILE)
-            server_context.set_alpn_protocols(['foo', 'bar'])
-            stats = server_params_test(client_context, server_context,
-                                       chatty=True, connectionchatty=True)
-            self.assertIs(stats['client_alpn_protocol'], None)
-
-        @unittest.skipUnless(ssl.HAS_ALPN, "ALPN support needed for this test")
-        def test_alpn_protocols(self):
-            server_protocols = ['foo', 'bar', 'milkshake']
-            protocol_tests = [
-                (['foo', 'bar'], 'foo'),
-                (['bar', 'foo'], 'foo'),
-                (['milkshake'], 'milkshake'),
-                (['http/3.0', 'http/4.0'], None)
-            ]
-            for client_protocols, expected in protocol_tests:
-                server_context = ssl.SSLContext(ssl.PROTOCOL_TLSv1_2)
-                server_context.load_cert_chain(CERTFILE)
-                server_context.set_alpn_protocols(server_protocols)
-                client_context = ssl.SSLContext(ssl.PROTOCOL_TLSv1_2)
-                client_context.load_cert_chain(CERTFILE)
-                client_context.set_alpn_protocols(client_protocols)
+            server_context.set_alpn_protocols(server_protocols)
+            client_context = ssl.SSLContext(ssl.PROTOCOL_TLSv1_2)
+            client_context.load_cert_chain(CERTFILE)
+            client_context.set_alpn_protocols(client_protocols)
 
-                try:
-                    stats = server_params_test(client_context,
-                                               server_context,
-                                               chatty=True,
-                                               connectionchatty=True)
-                except ssl.SSLError as e:
-                    stats = e
-
-                if (expected is None and IS_OPENSSL_1_1
-                        and ssl.OPENSSL_VERSION_INFO < (1, 1, 0, 6)):
-                    # OpenSSL 1.1.0 to 1.1.0e raises handshake error
-                    self.assertIsInstance(stats, ssl.SSLError)
-                else:
-                    msg = "failed trying %s (s) and %s (c).\n" \
-                        "was expecting %s, but got %%s from the %%s" \
-                            % (str(server_protocols), str(client_protocols),
-                                str(expected))
-                    client_result = stats['client_alpn_protocol']
-                    self.assertEqual(client_result, expected,
-                                     msg % (client_result, "client"))
-                    server_result = stats['server_alpn_protocols'][-1] \
-                        if len(stats['server_alpn_protocols']) else 'nothing'
-                    self.assertEqual(server_result, expected,
-                                     msg % (server_result, "server"))
-
-        def test_selected_npn_protocol(self):
-            # selected_npn_protocol() is None unless NPN is used
-            context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
-            context.load_cert_chain(CERTFILE)
-            stats = server_params_test(context, context,
-                                       chatty=True, connectionchatty=True)
-            self.assertIs(stats['client_npn_protocol'], None)
-
-        @unittest.skipUnless(ssl.HAS_NPN, "NPN support needed for this test")
-        def test_npn_protocols(self):
-            server_protocols = ['http/1.1', 'spdy/2']
-            protocol_tests = [
-                (['http/1.1', 'spdy/2'], 'http/1.1'),
-                (['spdy/2', 'http/1.1'], 'http/1.1'),
-                (['spdy/2', 'test'], 'spdy/2'),
-                (['abc', 'def'], 'abc')
-            ]
-            for client_protocols, expected in protocol_tests:
-                server_context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
-                server_context.load_cert_chain(CERTFILE)
-                server_context.set_npn_protocols(server_protocols)
-                client_context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
-                client_context.load_cert_chain(CERTFILE)
-                client_context.set_npn_protocols(client_protocols)
-                stats = server_params_test(client_context, server_context,
-                                           chatty=True, connectionchatty=True)
+            try:
+                stats = server_params_test(client_context,
+                                           server_context,
+                                           chatty=True,
+                                           connectionchatty=True)
+            except ssl.SSLError as e:
+                stats = e
 
+            if (expected is None and IS_OPENSSL_1_1
+                    and ssl.OPENSSL_VERSION_INFO < (1, 1, 0, 6)):
+                # OpenSSL 1.1.0 to 1.1.0e raises handshake error
+                self.assertIsInstance(stats, ssl.SSLError)
+            else:
                 msg = "failed trying %s (s) and %s (c).\n" \
-                      "was expecting %s, but got %%s from the %%s" \
-                          % (str(server_protocols), str(client_protocols),
-                             str(expected))
-                client_result = stats['client_npn_protocol']
-                self.assertEqual(client_result, expected, msg % (client_result, "client"))
-                server_result = stats['server_npn_protocols'][-1] \
-                    if len(stats['server_npn_protocols']) else 'nothing'
-                self.assertEqual(server_result, expected, msg % (server_result, "server"))
-
-        def sni_contexts(self):
+                    "was expecting %s, but got %%s from the %%s" \
+                        % (str(server_protocols), str(client_protocols),
+                            str(expected))
+                client_result = stats['client_alpn_protocol']
+                self.assertEqual(client_result, expected,
+                                 msg % (client_result, "client"))
+                server_result = stats['server_alpn_protocols'][-1] \
+                    if len(stats['server_alpn_protocols']) else 'nothing'
+                self.assertEqual(server_result, expected,
+                                 msg % (server_result, "server"))
+
+    def test_selected_npn_protocol(self):
+        # selected_npn_protocol() is None unless NPN is used
+        context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
+        context.load_cert_chain(CERTFILE)
+        stats = server_params_test(context, context,
+                                   chatty=True, connectionchatty=True)
+        self.assertIs(stats['client_npn_protocol'], None)
+
+    @unittest.skipUnless(ssl.HAS_NPN, "NPN support needed for this test")
+    def test_npn_protocols(self):
+        server_protocols = ['http/1.1', 'spdy/2']
+        protocol_tests = [
+            (['http/1.1', 'spdy/2'], 'http/1.1'),
+            (['spdy/2', 'http/1.1'], 'http/1.1'),
+            (['spdy/2', 'test'], 'spdy/2'),
+            (['abc', 'def'], 'abc')
+        ]
+        for client_protocols, expected in protocol_tests:
             server_context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
-            server_context.load_cert_chain(SIGNED_CERTFILE)
-            other_context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
-            other_context.load_cert_chain(SIGNED_CERTFILE2)
+            server_context.load_cert_chain(CERTFILE)
+            server_context.set_npn_protocols(server_protocols)
             client_context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
-            client_context.verify_mode = ssl.CERT_REQUIRED
-            client_context.load_verify_locations(SIGNING_CA)
-            return server_context, other_context, client_context
+            client_context.load_cert_chain(CERTFILE)
+            client_context.set_npn_protocols(client_protocols)
+            stats = server_params_test(client_context, server_context,
+                                       chatty=True, connectionchatty=True)
 
-        def check_common_name(self, stats, name):
-            cert = stats['peercert']
-            self.assertIn((('commonName', name),), cert['subject'])
+            msg = "failed trying %s (s) and %s (c).\n" \
+                  "was expecting %s, but got %%s from the %%s" \
+                      % (str(server_protocols), str(client_protocols),
+                         str(expected))
+            client_result = stats['client_npn_protocol']
+            self.assertEqual(client_result, expected, msg % (client_result, "client"))
+            server_result = stats['server_npn_protocols'][-1] \
+                if len(stats['server_npn_protocols']) else 'nothing'
+            self.assertEqual(server_result, expected, msg % (server_result, "server"))
+
+    def sni_contexts(self):
+        server_context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
+        server_context.load_cert_chain(SIGNED_CERTFILE)
+        other_context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
+        other_context.load_cert_chain(SIGNED_CERTFILE2)
+        client_context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
+        client_context.verify_mode = ssl.CERT_REQUIRED
+        client_context.load_verify_locations(SIGNING_CA)
+        return server_context, other_context, client_context
+
+    def check_common_name(self, stats, name):
+        cert = stats['peercert']
+        self.assertIn((('commonName', name),), cert['subject'])
+
+    @needs_sni
+    def test_sni_callback(self):
+        calls = []
+        server_context, other_context, client_context = self.sni_contexts()
+
+        def servername_cb(ssl_sock, server_name, initial_context):
+            calls.append((server_name, initial_context))
+            if server_name is not None:
+                ssl_sock.context = other_context
+        server_context.set_servername_callback(servername_cb)
+
+        stats = server_params_test(client_context, server_context,
+                                   chatty=True,
+                                   sni_name='supermessage')
+        # The hostname was fetched properly, and the certificate was
+        # changed for the connection.
+        self.assertEqual(calls, [("supermessage", server_context)])
+        # CERTFILE4 was selected
+        self.check_common_name(stats, 'fakehostname')
+
+        calls = []
+        # The callback is called with server_name=None
+        stats = server_params_test(client_context, server_context,
+                                   chatty=True,
+                                   sni_name=None)
+        self.assertEqual(calls, [(None, server_context)])
+        self.check_common_name(stats, 'localhost')
+
+        # Check disabling the callback
+        calls = []
+        server_context.set_servername_callback(None)
+
+        stats = server_params_test(client_context, server_context,
+                                   chatty=True,
+                                   sni_name='notfunny')
+        # Certificate didn't change
+        self.check_common_name(stats, 'localhost')
+        self.assertEqual(calls, [])
 
-        @needs_sni
-        def test_sni_callback(self):
-            calls = []
-            server_context, other_context, client_context = self.sni_contexts()
+    @needs_sni
+    def test_sni_callback_alert(self):
+        # Returning a TLS alert is reflected to the connecting client
+        server_context, other_context, client_context = self.sni_contexts()
 
-            def servername_cb(ssl_sock, server_name, initial_context):
-                calls.append((server_name, initial_context))
-                if server_name is not None:
-                    ssl_sock.context = other_context
-            server_context.set_servername_callback(servername_cb)
+        def cb_returning_alert(ssl_sock, server_name, initial_context):
+            return ssl.ALERT_DESCRIPTION_ACCESS_DENIED
+        server_context.set_servername_callback(cb_returning_alert)
 
+        with self.assertRaises(ssl.SSLError) as cm:
             stats = server_params_test(client_context, server_context,
-                                       chatty=True,
+                                       chatty=False,
                                        sni_name='supermessage')
-            # The hostname was fetched properly, and the certificate was
-            # changed for the connection.
-            self.assertEqual(calls, [("supermessage", server_context)])
-            # CERTFILE4 was selected
-            self.check_common_name(stats, 'fakehostname')
-
-            calls = []
-            # The callback is called with server_name=None
+        self.assertEqual(cm.exception.reason, 'TLSV1_ALERT_ACCESS_DENIED')
+
+    @needs_sni
+    def test_sni_callback_raising(self):
+        # Raising fails the connection with a TLS handshake failure alert.
+        server_context, other_context, client_context = self.sni_contexts()
+
+        def cb_raising(ssl_sock, server_name, initial_context):
+            1/0
+        server_context.set_servername_callback(cb_raising)
+
+        with self.assertRaises(ssl.SSLError) as cm, \
+             support.captured_stderr() as stderr:
             stats = server_params_test(client_context, server_context,
-                                       chatty=True,
-                                       sni_name=None)
-            self.assertEqual(calls, [(None, server_context)])
-            self.check_common_name(stats, 'localhost')
+                                       chatty=False,
+                                       sni_name='supermessage')
+        self.assertEqual(cm.exception.reason, 'SSLV3_ALERT_HANDSHAKE_FAILURE')
+        self.assertIn("ZeroDivisionError", stderr.getvalue())
+
+    @needs_sni
+    def test_sni_callback_wrong_return_type(self):
+        # Returning the wrong return type terminates the TLS connection
+        # with an internal error alert.
+        server_context, other_context, client_context = self.sni_contexts()
 
-            # Check disabling the callback
-            calls = []
-            server_context.set_servername_callback(None)
+        def cb_wrong_return_type(ssl_sock, server_name, initial_context):
+            return "foo"
+        server_context.set_servername_callback(cb_wrong_return_type)
 
+        with self.assertRaises(ssl.SSLError) as cm, \
+             support.captured_stderr() as stderr:
             stats = server_params_test(client_context, server_context,
-                                       chatty=True,
-                                       sni_name='notfunny')
-            # Certificate didn't change
-            self.check_common_name(stats, 'localhost')
-            self.assertEqual(calls, [])
-
-        @needs_sni
-        def test_sni_callback_alert(self):
-            # Returning a TLS alert is reflected to the connecting client
-            server_context, other_context, client_context = self.sni_contexts()
-
-            def cb_returning_alert(ssl_sock, server_name, initial_context):
-                return ssl.ALERT_DESCRIPTION_ACCESS_DENIED
-            server_context.set_servername_callback(cb_returning_alert)
-
-            with self.assertRaises(ssl.SSLError) as cm:
-                stats = server_params_test(client_context, server_context,
-                                           chatty=False,
-                                           sni_name='supermessage')
-            self.assertEqual(cm.exception.reason, 'TLSV1_ALERT_ACCESS_DENIED')
-
-        @needs_sni
-        def test_sni_callback_raising(self):
-            # Raising fails the connection with a TLS handshake failure alert.
-            server_context, other_context, client_context = self.sni_contexts()
-
-            def cb_raising(ssl_sock, server_name, initial_context):
-                1/0
-            server_context.set_servername_callback(cb_raising)
-
-            with self.assertRaises(ssl.SSLError) as cm, \
-                 support.captured_stderr() as stderr:
-                stats = server_params_test(client_context, server_context,
-                                           chatty=False,
-                                           sni_name='supermessage')
-            self.assertEqual(cm.exception.reason, 'SSLV3_ALERT_HANDSHAKE_FAILURE')
-            self.assertIn("ZeroDivisionError", stderr.getvalue())
-
-        @needs_sni
-        def test_sni_callback_wrong_return_type(self):
-            # Returning the wrong return type terminates the TLS connection
-            # with an internal error alert.
-            server_context, other_context, client_context = self.sni_contexts()
-
-            def cb_wrong_return_type(ssl_sock, server_name, initial_context):
-                return "foo"
-            server_context.set_servername_callback(cb_wrong_return_type)
-
-            with self.assertRaises(ssl.SSLError) as cm, \
-                 support.captured_stderr() as stderr:
-                stats = server_params_test(client_context, server_context,
-                                           chatty=False,
-                                           sni_name='supermessage')
-            self.assertEqual(cm.exception.reason, 'TLSV1_ALERT_INTERNAL_ERROR')
-            self.assertIn("TypeError", stderr.getvalue())
-
-        def test_shared_ciphers(self):
-            server_context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
-            server_context.load_cert_chain(SIGNED_CERTFILE)
-            client_context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
-            client_context.verify_mode = ssl.CERT_REQUIRED
-            client_context.load_verify_locations(SIGNING_CA)
-            if ssl.OPENSSL_VERSION_INFO >= (1, 0, 2):
-                client_context.set_ciphers("AES128:AES256")
-                server_context.set_ciphers("AES256")
-                alg1 = "AES256"
-                alg2 = "AES-256"
-            else:
-                client_context.set_ciphers("AES:3DES")
-                server_context.set_ciphers("3DES")
-                alg1 = "3DES"
-                alg2 = "DES-CBC3"
-
-            stats = server_params_test(client_context, server_context)
-            ciphers = stats['server_shared_ciphers'][0]
-            self.assertGreater(len(ciphers), 0)
-            for name, tls_version, bits in ciphers:
-                if not alg1 in name.split("-") and alg2 not in name:
-                    self.fail(name)
-
-        def test_read_write_after_close_raises_valuerror(self):
-            context = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
-            context.verify_mode = ssl.CERT_REQUIRED
-            context.load_verify_locations(CERTFILE)
-            context.load_cert_chain(CERTFILE)
-            server = ThreadedEchoServer(context=context, chatty=False)
-
-            with server:
-                s = context.wrap_socket(socket.socket())
+                                       chatty=False,
+                                       sni_name='supermessage')
+        self.assertEqual(cm.exception.reason, 'TLSV1_ALERT_INTERNAL_ERROR')
+        self.assertIn("TypeError", stderr.getvalue())
+
+    def test_shared_ciphers(self):
+        server_context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
+        server_context.load_cert_chain(SIGNED_CERTFILE)
+        client_context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
+        client_context.verify_mode = ssl.CERT_REQUIRED
+        client_context.load_verify_locations(SIGNING_CA)
+        if ssl.OPENSSL_VERSION_INFO >= (1, 0, 2):
+            client_context.set_ciphers("AES128:AES256")
+            server_context.set_ciphers("AES256")
+            alg1 = "AES256"
+            alg2 = "AES-256"
+        else:
+            client_context.set_ciphers("AES:3DES")
+            server_context.set_ciphers("3DES")
+            alg1 = "3DES"
+            alg2 = "DES-CBC3"
+
+        stats = server_params_test(client_context, server_context)
+        ciphers = stats['server_shared_ciphers'][0]
+        self.assertGreater(len(ciphers), 0)
+        for name, tls_version, bits in ciphers:
+            if not alg1 in name.split("-") and alg2 not in name:
+                self.fail(name)
+
+    def test_read_write_after_close_raises_valuerror(self):
+        context = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
+        context.verify_mode = ssl.CERT_REQUIRED
+        context.load_verify_locations(CERTFILE)
+        context.load_cert_chain(CERTFILE)
+        server = ThreadedEchoServer(context=context, chatty=False)
+
+        with server:
+            s = context.wrap_socket(socket.socket())
+            s.connect((HOST, server.port))
+            s.close()
+
+            self.assertRaises(ValueError, s.read, 1024)
+            self.assertRaises(ValueError, s.write, b'hello')
+
+    def test_sendfile(self):
+        TEST_DATA = b"x" * 512
+        with open(support.TESTFN, 'wb') as f:
+            f.write(TEST_DATA)
+        self.addCleanup(support.unlink, support.TESTFN)
+        context = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
+        context.verify_mode = ssl.CERT_REQUIRED
+        context.load_verify_locations(CERTFILE)
+        context.load_cert_chain(CERTFILE)
+        server = ThreadedEchoServer(context=context, chatty=False)
+        with server:
+            with context.wrap_socket(socket.socket()) as s:
                 s.connect((HOST, server.port))
-                s.close()
+                with open(support.TESTFN, 'rb') as file:
+                    s.sendfile(file)
+                    self.assertEqual(s.recv(1024), TEST_DATA)
+
+    def test_session(self):
+        server_context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
+        server_context.load_cert_chain(SIGNED_CERTFILE)
+        client_context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
+        client_context.verify_mode = ssl.CERT_REQUIRED
+        client_context.load_verify_locations(SIGNING_CA)
+
+        # first connection without session
+        stats = server_params_test(client_context, server_context)
+        session = stats['session']
+        self.assertTrue(session.id)
+        self.assertGreater(session.time, 0)
+        self.assertGreater(session.timeout, 0)
+        self.assertTrue(session.has_ticket)
+        if ssl.OPENSSL_VERSION_INFO > (1, 0, 1):
+            self.assertGreater(session.ticket_lifetime_hint, 0)
+        self.assertFalse(stats['session_reused'])
+        sess_stat = server_context.session_stats()
+        self.assertEqual(sess_stat['accept'], 1)
+        self.assertEqual(sess_stat['hits'], 0)
+
+        # reuse session
+        stats = server_params_test(client_context, server_context, session=session)
+        sess_stat = server_context.session_stats()
+        self.assertEqual(sess_stat['accept'], 2)
+        self.assertEqual(sess_stat['hits'], 1)
+        self.assertTrue(stats['session_reused'])
+        session2 = stats['session']
+        self.assertEqual(session2.id, session.id)
+        self.assertEqual(session2, session)
+        self.assertIsNot(session2, session)
+        self.assertGreaterEqual(session2.time, session.time)
+        self.assertGreaterEqual(session2.timeout, session.timeout)
+
+        # another one without session
+        stats = server_params_test(client_context, server_context)
+        self.assertFalse(stats['session_reused'])
+        session3 = stats['session']
+        self.assertNotEqual(session3.id, session.id)
+        self.assertNotEqual(session3, session)
+        sess_stat = server_context.session_stats()
+        self.assertEqual(sess_stat['accept'], 3)
+        self.assertEqual(sess_stat['hits'], 1)
+
+        # reuse session again
+        stats = server_params_test(client_context, server_context, session=session)
+        self.assertTrue(stats['session_reused'])
+        session4 = stats['session']
+        self.assertEqual(session4.id, session.id)
+        self.assertEqual(session4, session)
+        self.assertGreaterEqual(session4.time, session.time)
+        self.assertGreaterEqual(session4.timeout, session.timeout)
+        sess_stat = server_context.session_stats()
+        self.assertEqual(sess_stat['accept'], 4)
+        self.assertEqual(sess_stat['hits'], 2)
+
+    def test_session_handling(self):
+        context = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
+        context.verify_mode = ssl.CERT_REQUIRED
+        context.load_verify_locations(CERTFILE)
+        context.load_cert_chain(CERTFILE)
+
+        context2 = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
+        context2.verify_mode = ssl.CERT_REQUIRED
+        context2.load_verify_locations(CERTFILE)
+        context2.load_cert_chain(CERTFILE)
+
+        server = ThreadedEchoServer(context=context, chatty=False)
+        with server:
+            with context.wrap_socket(socket.socket()) as s:
+                # session is None before handshake
+                self.assertEqual(s.session, None)
+                self.assertEqual(s.session_reused, None)
+                s.connect((HOST, server.port))
+                session = s.session
+                self.assertTrue(session)
+                with self.assertRaises(TypeError) as e:
+                    s.session = object
+                self.assertEqual(str(e.exception), 'Value is not a SSLSession.')
 
-                self.assertRaises(ValueError, s.read, 1024)
-                self.assertRaises(ValueError, s.write, b'hello')
-
-        def test_sendfile(self):
-            TEST_DATA = b"x" * 512
-            with open(support.TESTFN, 'wb') as f:
-                f.write(TEST_DATA)
-            self.addCleanup(support.unlink, support.TESTFN)
-            context = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
-            context.verify_mode = ssl.CERT_REQUIRED
-            context.load_verify_locations(CERTFILE)
-            context.load_cert_chain(CERTFILE)
-            server = ThreadedEchoServer(context=context, chatty=False)
-            with server:
-                with context.wrap_socket(socket.socket()) as s:
-                    s.connect((HOST, server.port))
-                    with open(support.TESTFN, 'rb') as file:
-                        s.sendfile(file)
-                        self.assertEqual(s.recv(1024), TEST_DATA)
+            with context.wrap_socket(socket.socket()) as s:
+                s.connect((HOST, server.port))
+                # cannot set session after handshake
+                with self.assertRaises(ValueError) as e:
+                    s.session = session
+                self.assertEqual(str(e.exception),
+                                 'Cannot set session after handshake.')
 
-        def test_session(self):
-            server_context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
-            server_context.load_cert_chain(SIGNED_CERTFILE)
-            client_context = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
-            client_context.verify_mode = ssl.CERT_REQUIRED
-            client_context.load_verify_locations(SIGNING_CA)
-
-            # first connection without session
-            stats = server_params_test(client_context, server_context)
-            session = stats['session']
-            self.assertTrue(session.id)
-            self.assertGreater(session.time, 0)
-            self.assertGreater(session.timeout, 0)
-            self.assertTrue(session.has_ticket)
-            if ssl.OPENSSL_VERSION_INFO > (1, 0, 1):
-                self.assertGreater(session.ticket_lifetime_hint, 0)
-            self.assertFalse(stats['session_reused'])
-            sess_stat = server_context.session_stats()
-            self.assertEqual(sess_stat['accept'], 1)
-            self.assertEqual(sess_stat['hits'], 0)
-
-            # reuse session
-            stats = server_params_test(client_context, server_context, session=session)
-            sess_stat = server_context.session_stats()
-            self.assertEqual(sess_stat['accept'], 2)
-            self.assertEqual(sess_stat['hits'], 1)
-            self.assertTrue(stats['session_reused'])
-            session2 = stats['session']
-            self.assertEqual(session2.id, session.id)
-            self.assertEqual(session2, session)
-            self.assertIsNot(session2, session)
-            self.assertGreaterEqual(session2.time, session.time)
-            self.assertGreaterEqual(session2.timeout, session.timeout)
-
-            # another one without session
-            stats = server_params_test(client_context, server_context)
-            self.assertFalse(stats['session_reused'])
-            session3 = stats['session']
-            self.assertNotEqual(session3.id, session.id)
-            self.assertNotEqual(session3, session)
-            sess_stat = server_context.session_stats()
-            self.assertEqual(sess_stat['accept'], 3)
-            self.assertEqual(sess_stat['hits'], 1)
-
-            # reuse session again
-            stats = server_params_test(client_context, server_context, session=session)
-            self.assertTrue(stats['session_reused'])
-            session4 = stats['session']
-            self.assertEqual(session4.id, session.id)
-            self.assertEqual(session4, session)
-            self.assertGreaterEqual(session4.time, session.time)
-            self.assertGreaterEqual(session4.timeout, session.timeout)
-            sess_stat = server_context.session_stats()
-            self.assertEqual(sess_stat['accept'], 4)
-            self.assertEqual(sess_stat['hits'], 2)
-
-        def test_session_handling(self):
-            context = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
-            context.verify_mode = ssl.CERT_REQUIRED
-            context.load_verify_locations(CERTFILE)
-            context.load_cert_chain(CERTFILE)
-
-            context2 = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
-            context2.verify_mode = ssl.CERT_REQUIRED
-            context2.load_verify_locations(CERTFILE)
-            context2.load_cert_chain(CERTFILE)
-
-            server = ThreadedEchoServer(context=context, chatty=False)
-            with server:
-                with context.wrap_socket(socket.socket()) as s:
-                    # session is None before handshake
-                    self.assertEqual(s.session, None)
-                    self.assertEqual(s.session_reused, None)
-                    s.connect((HOST, server.port))
-                    session = s.session
-                    self.assertTrue(session)
-                    with self.assertRaises(TypeError) as e:
-                        s.session = object
-                    self.assertEqual(str(e.exception), 'Value is not a SSLSession.')
+            with context.wrap_socket(socket.socket()) as s:
+                # can set session before handshake and before the
+                # connection was established
+                s.session = session
+                s.connect((HOST, server.port))
+                self.assertEqual(s.session.id, session.id)
+                self.assertEqual(s.session, session)
+                self.assertEqual(s.session_reused, True)
 
-                with context.wrap_socket(socket.socket()) as s:
-                    s.connect((HOST, server.port))
-                    # cannot set session after handshake
-                    with self.assertRaises(ValueError) as e:
-                        s.session = session
-                    self.assertEqual(str(e.exception),
-                                     'Cannot set session after handshake.')
-
-                with context.wrap_socket(socket.socket()) as s:
-                    # can set session before handshake and before the
-                    # connection was established
+            with context2.wrap_socket(socket.socket()) as s:
+                # cannot re-use session with a different SSLContext
+                with self.assertRaises(ValueError) as e:
                     s.session = session
                     s.connect((HOST, server.port))
-                    self.assertEqual(s.session.id, session.id)
-                    self.assertEqual(s.session, session)
-                    self.assertEqual(s.session_reused, True)
-
-                with context2.wrap_socket(socket.socket()) as s:
-                    # cannot re-use session with a different SSLContext
-                    with self.assertRaises(ValueError) as e:
-                        s.session = session
-                        s.connect((HOST, server.port))
-                    self.assertEqual(str(e.exception),
-                                     'Session refers to a different SSLContext.')
+                self.assertEqual(str(e.exception),
+                                 'Session refers to a different SSLContext.')
 
 
 def test_main(verbose=False):
@@ -3610,22 +3603,17 @@ def test_main(verbose=False):
 
     tests = [
         ContextTests, BasicSocketTests, SSLErrorTests, MemoryBIOTests,
-        SimpleBackgroundTests,
+        SimpleBackgroundTests, ThreadedTests,
     ]
 
     if support.is_resource_enabled('network'):
         tests.append(NetworkedTests)
 
-    if _have_threads:
-        thread_info = support.threading_setup()
-        if thread_info:
-            tests.append(ThreadedTests)
-
+    thread_info = support.threading_setup()
     try:
         support.run_unittest(*tests)
     finally:
-        if _have_threads:
-            support.threading_cleanup(*thread_info)
+        support.threading_cleanup(*thread_info)
 
 if __name__ == "__main__":
     test_main()
diff --git a/Lib/test/test_subprocess.py b/Lib/test/test_subprocess.py
index b7079b1..10ef87b 100644
--- a/Lib/test/test_subprocess.py
+++ b/Lib/test/test_subprocess.py
@@ -14,6 +14,7 @@ import selectors
 import sysconfig
 import select
 import shutil
+import threading
 import gc
 import textwrap
 
@@ -25,11 +26,6 @@ else:
     import ctypes.util
 
 try:
-    import threading
-except ImportError:
-    threading = None
-
-try:
     import _testcapi
 except ImportError:
     _testcapi = None
@@ -1196,7 +1192,6 @@ class ProcessTestCase(BaseTestCase):
         self.assertEqual(stderr, "")
         self.assertEqual(proc.returncode, 0)
 
-    @unittest.skipIf(threading is None, "threading required")
     def test_double_close_on_error(self):
         # Issue #18851
         fds = []
@@ -1226,7 +1221,6 @@ class ProcessTestCase(BaseTestCase):
             if exc is not None:
                 raise exc
 
-    @unittest.skipIf(threading is None, "threading required")
     def test_threadsafe_wait(self):
         """Issue21291: Popen.wait() needs to be threadsafe for returncode."""
         proc = subprocess.Popen([sys.executable, '-c',
diff --git a/Lib/test/test_sys.py b/Lib/test/test_sys.py
index 3844812..04550e5 100644
--- a/Lib/test/test_sys.py
+++ b/Lib/test/test_sys.py
@@ -10,15 +10,12 @@ import codecs
 import gc
 import sysconfig
 import locale
+import threading
 
 # count the number of test runs, used to create unique
 # strings to intern in test_intern()
 numruns = 0
 
-try:
-    import threading
-except ImportError:
-    threading = None
 
 class SysModuleTest(unittest.TestCase):
 
@@ -172,7 +169,6 @@ class SysModuleTest(unittest.TestCase):
                 sys.setcheckinterval(n)
                 self.assertEqual(sys.getcheckinterval(), n)
 
-    @unittest.skipUnless(threading, 'Threading required for this test.')
     def test_switchinterval(self):
         self.assertRaises(TypeError, sys.setswitchinterval)
         self.assertRaises(TypeError, sys.setswitchinterval, "a")
@@ -348,21 +344,8 @@ class SysModuleTest(unittest.TestCase):
         )
 
     # sys._current_frames() is a CPython-only gimmick.
-    def test_current_frames(self):
-        have_threads = True
-        try:
-            import _thread
-        except ImportError:
-            have_threads = False
-
-        if have_threads:
-            self.current_frames_with_threads()
-        else:
-            self.current_frames_without_threads()
-
-    # Test sys._current_frames() in a WITH_THREADS build.
     @test.support.reap_threads
-    def current_frames_with_threads(self):
+    def test_current_frames(self):
         import threading
         import traceback
 
@@ -426,15 +409,6 @@ class SysModuleTest(unittest.TestCase):
         leave_g.set()
         t.join()
 
-    # Test sys._current_frames() when thread support doesn't exist.
-    def current_frames_without_threads(self):
-        # Not much happens here:  there is only one thread, with artificial
-        # "thread id" 0.
-        d = sys._current_frames()
-        self.assertEqual(len(d), 1)
-        self.assertIn(0, d)
-        self.assertTrue(d[0] is sys._getframe())
-
     def test_attributes(self):
         self.assertIsInstance(sys.api_version, int)
         self.assertIsInstance(sys.argv, list)
@@ -516,8 +490,6 @@ class SysModuleTest(unittest.TestCase):
         if not sys.platform.startswith('win'):
             self.assertIsInstance(sys.abiflags, str)
 
-    @unittest.skipUnless(hasattr(sys, 'thread_info'),
-                         'Threading required for this test.')
     def test_thread_info(self):
         info = sys.thread_info
         self.assertEqual(len(info), 3)
diff --git a/Lib/test/test_telnetlib.py b/Lib/test/test_telnetlib.py
index 51d82e1..414c328 100644
--- a/Lib/test/test_telnetlib.py
+++ b/Lib/test/test_telnetlib.py
@@ -1,11 +1,11 @@
 import socket
 import selectors
 import telnetlib
+import threading
 import contextlib
 
 from test import support
 import unittest
-threading = support.import_module('threading')
 
 HOST = support.HOST
 
diff --git a/Lib/test/test_threaded_import.py b/Lib/test/test_threaded_import.py
index 75c66b0..035344b 100644
--- a/Lib/test/test_threaded_import.py
+++ b/Lib/test/test_threaded_import.py
@@ -11,12 +11,12 @@ import importlib
 import sys
 import time
 import shutil
+import threading
 import unittest
 from unittest import mock
 from test.support import (
     verbose, import_module, run_unittest, TESTFN, reap_threads,
     forget, unlink, rmtree, start_threads)
-threading = import_module('threading')
 
 def task(N, done, done_tasks, errors):
     try:
diff --git a/Lib/test/test_threadedtempfile.py b/Lib/test/test_threadedtempfile.py
index b742036..f3d4ba3 100644
--- a/Lib/test/test_threadedtempfile.py
+++ b/Lib/test/test_threadedtempfile.py
@@ -19,9 +19,9 @@ FILES_PER_THREAD = 50
 import tempfile
 
 from test.support import start_threads, import_module
-threading = import_module('threading')
 import unittest
 import io
+import threading
 from traceback import print_exc
 
 startEvent = threading.Event()
diff --git a/Lib/test/test_threading.py b/Lib/test/test_threading.py
index 800d26f..912eb3f 100644
--- a/Lib/test/test_threading.py
+++ b/Lib/test/test_threading.py
@@ -9,8 +9,8 @@ from test.support.script_helper import assert_python_ok, assert_python_failure
 
 import random
 import sys
-_thread = import_module('_thread')
-threading = import_module('threading')
+import _thread
+import threading
 import time
 import unittest
 import weakref
diff --git a/Lib/test/test_threading_local.py b/Lib/test/test_threading_local.py
index 4092cf3..984f8dd 100644
--- a/Lib/test/test_threading_local.py
+++ b/Lib/test/test_threading_local.py
@@ -5,8 +5,8 @@ import weakref
 import gc
 
 # Modules under test
-_thread = support.import_module('_thread')
-threading = support.import_module('threading')
+import _thread
+import threading
 import _threading_local
 
 
diff --git a/Lib/test/test_time.py b/Lib/test/test_time.py
index 810ec37..42323b9 100644
--- a/Lib/test/test_time.py
+++ b/Lib/test/test_time.py
@@ -9,10 +9,6 @@ import sysconfig
 import time
 import unittest
 try:
-    import threading
-except ImportError:
-    threading = None
-try:
     import _testcapi
 except ImportError:
     _testcapi = None
diff --git a/Lib/test/test_tracemalloc.py b/Lib/test/test_tracemalloc.py
index 742259b..780942a 100644
--- a/Lib/test/test_tracemalloc.py
+++ b/Lib/test/test_tracemalloc.py
@@ -7,10 +7,7 @@ from unittest.mock import patch
 from test.support.script_helper import (assert_python_ok, assert_python_failure,
                                         interpreter_requires_environment)
 from test import support
-try:
-    import threading
-except ImportError:
-    threading = None
+
 try:
     import _testcapi
 except ImportError:
diff --git a/Lib/test/test_urllib2_localnet.py b/Lib/test/test_urllib2_localnet.py
index f83f9cc..741d136 100644
--- a/Lib/test/test_urllib2_localnet.py
+++ b/Lib/test/test_urllib2_localnet.py
@@ -4,13 +4,12 @@ import email
 import urllib.parse
 import urllib.request
 import http.server
+import threading
 import unittest
 import hashlib
 
 from test import support
 
-threading = support.import_module('threading')
-
 try:
     import ssl
 except ImportError:
@@ -276,7 +275,6 @@ class FakeProxyHandler(http.server.BaseHTTPRequestHandler):
 
 # Test cases
 
-@unittest.skipUnless(threading, "Threading required for this test.")
 class BasicAuthTests(unittest.TestCase):
     USER = "testUser"
     PASSWD = "testPass"
@@ -317,7 +315,6 @@ class BasicAuthTests(unittest.TestCase):
         self.assertRaises(urllib.error.HTTPError, urllib.request.urlopen, self.server_url)
 
 
-@unittest.skipUnless(threading, "Threading required for this test.")
 class ProxyAuthTests(unittest.TestCase):
     URL = "http://localhost"
 
@@ -439,7 +436,6 @@ def GetRequestHandler(responses):
     return FakeHTTPRequestHandler
 
 
-@unittest.skipUnless(threading, "Threading required for this test.")
 class TestUrlopen(unittest.TestCase):
     """Tests urllib.request.urlopen using the network.
 
diff --git a/Lib/test/test_venv.py b/Lib/test/test_venv.py
index 2691632..aac010b 100644
--- a/Lib/test/test_venv.py
+++ b/Lib/test/test_venv.py
@@ -15,15 +15,10 @@ import sys
 import tempfile
 from test.support import (captured_stdout, captured_stderr,
                           can_symlink, EnvironmentVarGuard, rmtree)
+import threading
 import unittest
 import venv
 
-
-try:
-    import threading
-except ImportError:
-    threading = None
-
 try:
     import ctypes
 except ImportError:
@@ -420,8 +415,6 @@ class EnsurePipTest(BaseTest):
         if not system_site_packages:
             self.assert_pip_not_installed()
 
-    @unittest.skipUnless(threading, 'some dependencies of pip import threading'
-                                    ' module unconditionally')
     # Issue #26610: pip/pep425tags.py requires ctypes
     @unittest.skipUnless(ctypes, 'pip requires ctypes')
     def test_with_pip(self):
diff --git a/Lib/test/test_weakref.py b/Lib/test/test_weakref.py
index 43cf2c0..0384a9f 100644
--- a/Lib/test/test_weakref.py
+++ b/Lib/test/test_weakref.py
@@ -6,6 +6,7 @@ import weakref
 import operator
 import contextlib
 import copy
+import threading
 import time
 
 from test import support
@@ -78,7 +79,6 @@ def collect_in_thread(period=0.0001):
     """
     Ensure GC collections happen in a different thread, at a high frequency.
     """
-    threading = support.import_module('threading')
     please_stop = False
 
     def collect():
diff --git a/Lib/test/test_xmlrpc.py b/Lib/test/test_xmlrpc.py
index a609eef..f2b496a 100644
--- a/Lib/test/test_xmlrpc.py
+++ b/Lib/test/test_xmlrpc.py
@@ -10,6 +10,7 @@ import xmlrpc.server
 import http.client
 import http, http.server
 import socket
+import threading
 import re
 import io
 import contextlib
@@ -19,10 +20,6 @@ try:
     import gzip
 except ImportError:
     gzip = None
-try:
-    import threading
-except ImportError:
-    threading = None
 
 alist = [{'astring': 'foo@bar.baz.spam',
           'afloat': 7283.43,
@@ -307,7 +304,6 @@ class XMLRPCTestCase(unittest.TestCase):
         except OSError:
             self.assertTrue(has_ssl)
 
-    @unittest.skipUnless(threading, "Threading required for this test.")
     def test_keepalive_disconnect(self):
         class RequestHandler(http.server.BaseHTTPRequestHandler):
             protocol_version = "HTTP/1.1"
@@ -747,7 +743,6 @@ def make_request_and_skipIf(condition, reason):
         return make_request_and_skip
     return decorator
 
-@unittest.skipUnless(threading, 'Threading required for this test.')
 class BaseServerTestCase(unittest.TestCase):
     requestHandler = None
     request_count = 1
@@ -1206,7 +1201,6 @@ class FailingMessageClass(http.client.HTTPMessage):
         return super().get(key, failobj)
 
 
-@unittest.skipUnless(threading, 'Threading required for this test.')
 class FailingServerTestCase(unittest.TestCase):
     def setUp(self):
         self.evt = threading.Event()
diff --git a/Lib/threading.py b/Lib/threading.py
index 06dbc68..e4bf974 100644
--- a/Lib/threading.py
+++ b/Lib/threading.py
@@ -990,38 +990,12 @@ class Thread:
 
     def _delete(self):
         "Remove current thread from the dict of currently running threads."
-
-        # Notes about running with _dummy_thread:
-        #
-        # Must take care to not raise an exception if _dummy_thread is being
-        # used (and thus this module is being used as an instance of
-        # dummy_threading).  _dummy_thread.get_ident() always returns 1 since
-        # there is only one thread if _dummy_thread is being used.  Thus
-        # len(_active) is always <= 1 here, and any Thread instance created
-        # overwrites the (if any) thread currently registered in _active.
-        #
-        # An instance of _MainThread is always created by 'threading'.  This
-        # gets overwritten the instant an instance of Thread is created; both
-        # threads return 1 from _dummy_thread.get_ident() and thus have the
-        # same key in the dict.  So when the _MainThread instance created by
-        # 'threading' tries to clean itself up when atexit calls this method
-        # it gets a KeyError if another Thread instance was created.
-        #
-        # This all means that KeyError from trying to delete something from
-        # _active if dummy_threading is being used is a red herring.  But
-        # since it isn't if dummy_threading is *not* being used then don't
-        # hide the exception.
-
-        try:
-            with _active_limbo_lock:
-                del _active[get_ident()]
-                # There must not be any python code between the previous line
-                # and after the lock is released.  Otherwise a tracing function
-                # could try to acquire the lock again in the same thread, (in
-                # current_thread()), and would block.
-        except KeyError:
-            if 'dummy_threading' not in _sys.modules:
-                raise
+        with _active_limbo_lock:
+            del _active[get_ident()]
+            # There must not be any python code between the previous line
+            # and after the lock is released.  Otherwise a tracing function
+            # could try to acquire the lock again in the same thread, (in
+            # current_thread()), and would block.
 
     def join(self, timeout=None):
         """Wait until the thread terminates.
diff --git a/Lib/trace.py b/Lib/trace.py
index e443edd..48a1d1b 100755
--- a/Lib/trace.py
+++ b/Lib/trace.py
@@ -61,21 +61,15 @@ import dis
 import pickle
 from time import monotonic as _time
 
-try:
-    import threading
-except ImportError:
-    _settrace = sys.settrace
-
-    def _unsettrace():
-        sys.settrace(None)
-else:
-    def _settrace(func):
-        threading.settrace(func)
-        sys.settrace(func)
-
-    def _unsettrace():
-        sys.settrace(None)
-        threading.settrace(None)
+import threading
+
+def _settrace(func):
+    threading.settrace(func)
+    sys.settrace(func)
+
+def _unsettrace():
+    sys.settrace(None)
+    threading.settrace(None)
 
 PRAGMA_NOCOVER = "#pragma NO COVER"
 
diff --git a/Lib/zipfile.py b/Lib/zipfile.py
index cc46a6c..37ce328 100644
--- a/Lib/zipfile.py
+++ b/Lib/zipfile.py
@@ -12,11 +12,7 @@ import stat
 import shutil
 import struct
 import binascii
-
-try:
-    import threading
-except ImportError:
-    import dummy_threading as threading
+import threading
 
 try:
     import zlib # We may need its compression method