[3.10] bpo-44498: Issue a deprecation warning on asynchat, asyncore and smtpd import (GH-26882) (GH-26904)

* Issue a deprecation warning on smtpd import

* Also issue DeprecationWarnings for asynchat and asyncore

* Fix some tests

* test___all__ requires the word 'module' or 'package' in the deprecation
  warning text, so add those to smtpd, asynchat, and asyncore.
* In test_support, use pprint now instead of asyncore as the landmark.

* Add What's New

* Use ..deprecated::

* Use ..deprecated::

* Update Lib/smtpd.py

Co-authored-by: Miro Hrončok <miro@hroncok.cz>

* Update Doc/library/smtpd.rst

Co-authored-by: Miro Hrončok <miro@hroncok.cz>

* Import async{hat,ore} after the DeprecationWarning for this module

Co-authored-by: Miro Hrončok <miro@hroncok.cz>
(cherry picked from commit 8488b85c6397fe58f17fc00e047044c959ac0b04)


Co-authored-by: Barry Warsaw <barry@python.org>

Automerge-Triggered-By: GH:warsaw

4 files changed, 30 insertions, 4 deletions

diff --git a/Lib/asynchat.py b/Lib/asynchat.py
index f4ba361..de26ffa 100644
--- a/Lib/asynchat.py
+++ b/Lib/asynchat.py
@@ -48,6 +48,14 @@ you - by calling your self.found_terminator() method.
 import asyncore
 from collections import deque
 
+from warnings import warn
+warn(
+    'The asynchat module is deprecated. '
+    'The recommended replacement is asyncio',
+    DeprecationWarning,
+    stacklevel=2)
+
+
 
 class async_chat(asyncore.dispatcher):
     """This is an abstract class.  You must derive from this class, and add
diff --git a/Lib/asyncore.py b/Lib/asyncore.py
index eeea488..b1eea4b 100644
--- a/Lib/asyncore.py
+++ b/Lib/asyncore.py
@@ -57,6 +57,13 @@ from errno import EALREADY, EINPROGRESS, EWOULDBLOCK, ECONNRESET, EINVAL, \
      ENOTCONN, ESHUTDOWN, EISCONN, EBADF, ECONNABORTED, EPIPE, EAGAIN, \
      errorcode
 
+warnings.warn(
+    'The asyncore module is deprecated. '
+    'The recommended replacement is asyncio',
+    DeprecationWarning,
+    stacklevel=2)
+
+
 _DISCONNECTED = frozenset({ECONNRESET, ENOTCONN, ESHUTDOWN, ECONNABORTED, EPIPE,
                            EBADF})
 
diff --git a/Lib/smtpd.py b/Lib/smtpd.py
index 1e2adc8..bc43331 100755
--- a/Lib/smtpd.py
+++ b/Lib/smtpd.py
@@ -83,8 +83,6 @@ import errno
 import getopt
 import time
 import socket
-import asyncore
-import asynchat
 import collections
 from warnings import warn
 from email._header_value_parser import get_addr_spec, get_angle_addr
@@ -94,6 +92,19 @@ __all__ = [
     "MailmanProxy",
 ]
 
+warn(
+    'The smtpd module is deprecated and unmaintained.  Please see aiosmtpd '
+    '(https://aiosmtpd.readthedocs.io/) for the recommended replacement.',
+    DeprecationWarning,
+    stacklevel=2)
+
+
+# These are imported after the above warning so that users get the correct
+# deprecation warning.
+import asyncore
+import asynchat
+
+
 program = sys.argv[0]
 __version__ = 'Python SMTP proxy version 0.3'
 
diff --git a/Lib/test/test_support.py b/Lib/test/test_support.py
index 55d78b7..b1d3411 100644
--- a/Lib/test/test_support.py
+++ b/Lib/test/test_support.py
@@ -292,8 +292,8 @@ class TestSupport(unittest.TestCase):
 
     def test_CleanImport(self):
         import importlib
-        with import_helper.CleanImport("asyncore"):
-            importlib.import_module("asyncore")
+        with import_helper.CleanImport("pprint"):
+            importlib.import_module("pprint")
 
     def test_DirsOnSysPath(self):
         with import_helper.DirsOnSysPath('foo', 'bar'):