Remove binding of captured exceptions when not used to reduce the chances of creating cycles (GH-17246)

Capturing exceptions into names can lead to reference cycles though the __traceback__ attribute of the exceptions in some obscure cases that have been reported previously and fixed individually. As these variables are not used anyway, we can remove the binding to reduce the chances of creating reference cycles.

See for example GH-13135

28 files changed, 39 insertions, 39 deletions

diff --git a/Lib/asynchat.py b/Lib/asynchat.py
index fc1146a..f4ba361 100644
--- a/Lib/asynchat.py
+++ b/Lib/asynchat.py
@@ -117,7 +117,7 @@ class async_chat(asyncore.dispatcher):
             data = self.recv(self.ac_in_buffer_size)
         except BlockingIOError:
             return
-        except OSError as why:
+        except OSError:
             self.handle_error()
             return
 
diff --git a/Lib/asyncio/proactor_events.py b/Lib/asyncio/proactor_events.py
index 830d8ed..8338449 100644
--- a/Lib/asyncio/proactor_events.py
+++ b/Lib/asyncio/proactor_events.py
@@ -711,7 +711,7 @@ class BaseProactorEventLoop(base_events.BaseEventLoop):
             raise exceptions.SendfileNotAvailableError("not a regular file")
         try:
             fsize = os.fstat(fileno).st_size
-        except OSError as err:
+        except OSError:
             raise exceptions.SendfileNotAvailableError("not a regular file")
         blocksize = count if count else fsize
         if not blocksize:
diff --git a/Lib/asyncio/unix_events.py b/Lib/asyncio/unix_events.py
index 6621372..632546a 100644
--- a/Lib/asyncio/unix_events.py
+++ b/Lib/asyncio/unix_events.py
@@ -330,7 +330,7 @@ class _UnixSelectorEventLoop(selector_events.BaseSelectorEventLoop):
     async def _sock_sendfile_native(self, sock, file, offset, count):
         try:
             os.sendfile
-        except AttributeError as exc:
+        except AttributeError:
             raise exceptions.SendfileNotAvailableError(
                 "os.sendfile() is not available")
         try:
@@ -339,7 +339,7 @@ class _UnixSelectorEventLoop(selector_events.BaseSelectorEventLoop):
             raise exceptions.SendfileNotAvailableError("not a regular file")
         try:
             fsize = os.fstat(fileno).st_size
-        except OSError as err:
+        except OSError:
             raise exceptions.SendfileNotAvailableError("not a regular file")
         blocksize = count if count else fsize
         if not blocksize:
diff --git a/Lib/codeop.py b/Lib/codeop.py
index e5c7ade..fc7e1e7 100644
--- a/Lib/codeop.py
+++ b/Lib/codeop.py
@@ -80,7 +80,7 @@ def _maybe_compile(compiler, source, filename, symbol):
 
     try:
         code = compiler(source, filename, symbol)
-    except SyntaxError as err:
+    except SyntaxError:
         pass
 
     try:
diff --git a/Lib/ctypes/util.py b/Lib/ctypes/util.py
index 97973bc..01176bf 100644
--- a/Lib/ctypes/util.py
+++ b/Lib/ctypes/util.py
@@ -302,7 +302,7 @@ elif os.name == "posix":
                 res = re.search(expr, os.fsdecode(out))
                 if res:
                     result = res.group(0)
-            except Exception as e:
+            except Exception:
                 pass  # result will be None
             return result
 
diff --git a/Lib/enum.py b/Lib/enum.py
index 8a6e5d2..06f42a9 100644
--- a/Lib/enum.py
+++ b/Lib/enum.py
@@ -420,7 +420,7 @@ class EnumMeta(type):
         if module is None:
             try:
                 module = sys._getframe(2).f_globals['__name__']
-            except (AttributeError, ValueError, KeyError) as exc:
+            except (AttributeError, ValueError, KeyError):
                 pass
         if module is None:
             _make_class_unpicklable(enum_class)
diff --git a/Lib/filecmp.py b/Lib/filecmp.py
index e5ad839..cfdca1e 100644
--- a/Lib/filecmp.py
+++ b/Lib/filecmp.py
@@ -156,12 +156,12 @@ class dircmp:
             ok = 1
             try:
                 a_stat = os.stat(a_path)
-            except OSError as why:
+            except OSError:
                 # print('Can\'t stat', a_path, ':', why.args[1])
                 ok = 0
             try:
                 b_stat = os.stat(b_path)
-            except OSError as why:
+            except OSError:
                 # print('Can\'t stat', b_path, ':', why.args[1])
                 ok = 0
 
diff --git a/Lib/getpass.py b/Lib/getpass.py
index 36e17e4..6911f41 100644
--- a/Lib/getpass.py
+++ b/Lib/getpass.py
@@ -52,7 +52,7 @@ def unix_getpass(prompt='Password: ', stream=None):
             stack.enter_context(input)
             if not stream:
                 stream = input
-        except OSError as e:
+        except OSError:
             # If that fails, see if stdin can be controlled.
             stack.close()
             try:
diff --git a/Lib/importlib/abc.py b/Lib/importlib/abc.py
index 4b2d3de..b1b5ccc 100644
--- a/Lib/importlib/abc.py
+++ b/Lib/importlib/abc.py
@@ -10,7 +10,7 @@ except ImportError as exc:
     _frozen_importlib = None
 try:
     import _frozen_importlib_external
-except ImportError as exc:
+except ImportError:
     _frozen_importlib_external = _bootstrap_external
 import abc
 import warnings
diff --git a/Lib/lib2to3/main.py b/Lib/lib2to3/main.py
index d6b7088..c51626b 100644
--- a/Lib/lib2to3/main.py
+++ b/Lib/lib2to3/main.py
@@ -90,11 +90,11 @@ class StdoutRefactoringTool(refactor.MultiprocessRefactoringTool):
             if os.path.lexists(backup):
                 try:
                     os.remove(backup)
-                except OSError as err:
+                except OSError:
                     self.log_message("Can't remove backup %s", backup)
             try:
                 os.rename(filename, backup)
-            except OSError as err:
+            except OSError:
                 self.log_message("Can't rename %s to %s", filename, backup)
         # Actually write the new file
         write = super(StdoutRefactoringTool, self).write_file
diff --git a/Lib/msilib/__init__.py b/Lib/msilib/__init__.py
index 0bc8dd9..0e85aa2 100644
--- a/Lib/msilib/__init__.py
+++ b/Lib/msilib/__init__.py
@@ -116,7 +116,7 @@ def add_data(db, table, values):
                 raise TypeError("Unsupported type %s" % field.__class__.__name__)
         try:
             v.Modify(MSIMODIFY_INSERT, r)
-        except Exception as e:
+        except Exception:
             raise MSIError("Could not insert "+repr(values)+" into "+table)
 
         r.ClearData()
diff --git a/Lib/multiprocessing/managers.py b/Lib/multiprocessing/managers.py
index 75b5150..1f9c2da 100644
--- a/Lib/multiprocessing/managers.py
+++ b/Lib/multiprocessing/managers.py
@@ -248,7 +248,7 @@ class Server(object):
                     try:
                         obj, exposed, gettypeid = \
                             self.id_to_local_proxy_obj[ident]
-                    except KeyError as second_ke:
+                    except KeyError:
                         raise ke
 
                 if methodname not in exposed:
@@ -296,7 +296,7 @@ class Server(object):
             try:
                 try:
                     send(msg)
-                except Exception as e:
+                except Exception:
                     send(('#UNSERIALIZABLE', format_exc()))
             except Exception as e:
                 util.info('exception in thread serving %r',
diff --git a/Lib/multiprocessing/popen_fork.py b/Lib/multiprocessing/popen_fork.py
index 11e2160..a65b06f 100644
--- a/Lib/multiprocessing/popen_fork.py
+++ b/Lib/multiprocessing/popen_fork.py
@@ -25,7 +25,7 @@ class Popen(object):
         if self.returncode is None:
             try:
                 pid, sts = os.waitpid(self.pid, flag)
-            except OSError as e:
+            except OSError:
                 # Child process not yet created. See #1731717
                 # e.errno == errno.ECHILD == 10
                 return None
diff --git a/Lib/poplib.py b/Lib/poplib.py
index e3bd2ab..0b6750d 100644
--- a/Lib/poplib.py
+++ b/Lib/poplib.py
@@ -385,7 +385,7 @@ class POP3:
             for capline in rawcaps:
                 capnm, capargs = _parsecap(capline)
                 caps[capnm] = capargs
-        except error_proto as _err:
+        except error_proto:
             raise error_proto('-ERR CAPA not supported by server')
         return caps
 
diff --git a/Lib/test/pythoninfo.py b/Lib/test/pythoninfo.py
index 797b3af..eab82c3 100644
--- a/Lib/test/pythoninfo.py
+++ b/Lib/test/pythoninfo.py
@@ -754,7 +754,7 @@ def collect_info(info):
     ):
         try:
             collect_func(info_add)
-        except Exception as exc:
+        except Exception:
             error = True
             print("ERROR: %s() failed" % (collect_func.__name__),
                   file=sys.stderr)
diff --git a/Lib/test/test_cgitb.py b/Lib/test/test_cgitb.py
index e299ec3..8991bc1 100644
--- a/Lib/test/test_cgitb.py
+++ b/Lib/test/test_cgitb.py
@@ -31,7 +31,7 @@ class TestCgitb(unittest.TestCase):
     def test_text(self):
         try:
             raise ValueError("Hello World")
-        except ValueError as err:
+        except ValueError:
             text = cgitb.text(sys.exc_info())
             self.assertIn("ValueError", text)
             self.assertIn("Hello World", text)
diff --git a/Lib/test/test_class.py b/Lib/test/test_class.py
index 456f1be..7524f58 100644
--- a/Lib/test/test_class.py
+++ b/Lib/test/test_class.py
@@ -529,7 +529,7 @@ class ClassTests(unittest.TestCase):
             # In debug mode, printed XXX undetected error and
             #  raises AttributeError
             I()
-        except AttributeError as x:
+        except AttributeError:
             pass
         else:
             self.fail("attribute error for I.__init__ got masked")
diff --git a/Lib/test/test_codecs.py b/Lib/test/test_codecs.py
index e1638c1..3aec34c 100644
--- a/Lib/test/test_codecs.py
+++ b/Lib/test/test_codecs.py
@@ -11,7 +11,7 @@ from test import support
 
 try:
     import _testcapi
-except ImportError as exc:
+except ImportError:
     _testcapi = None
 
 try:
diff --git a/Lib/test/test_decimal.py b/Lib/test/test_decimal.py
index 1f37b53..fe0cfc7 100644
--- a/Lib/test/test_decimal.py
+++ b/Lib/test/test_decimal.py
@@ -5600,13 +5600,13 @@ class SignatureTest(unittest.TestCase):
                     args, kwds = mkargs(C, c_sig)
                     try:
                         getattr(c_type(9), attr)(*args, **kwds)
-                    except Exception as err:
+                    except Exception:
                         raise TestFailed("invalid signature for %s: %s %s" % (c_func, args, kwds))
 
                     args, kwds = mkargs(P, p_sig)
                     try:
                         getattr(p_type(9), attr)(*args, **kwds)
-                    except Exception as err:
+                    except Exception:
                         raise TestFailed("invalid signature for %s: %s %s" % (p_func, args, kwds))
 
         doit('Decimal')
diff --git a/Lib/test/test_ftplib.py b/Lib/test/test_ftplib.py
index b0e4641..b8eef82 100644
--- a/Lib/test/test_ftplib.py
+++ b/Lib/test/test_ftplib.py
@@ -346,7 +346,7 @@ if ssl is not None:
                 if err.args[0] in (ssl.SSL_ERROR_WANT_READ,
                                    ssl.SSL_ERROR_WANT_WRITE):
                     return
-            except OSError as err:
+            except OSError:
                 # Any "socket error" corresponds to a SSL_ERROR_SYSCALL return
                 # from OpenSSL's SSL_shutdown(), corresponding to a
                 # closed socket condition. See also:
diff --git a/Lib/test/test_sys_settrace.py b/Lib/test/test_sys_settrace.py
index fdd7894..d4e1ac2 100644
--- a/Lib/test/test_sys_settrace.py
+++ b/Lib/test/test_sys_settrace.py
@@ -161,8 +161,8 @@ def raises():
 def test_raise():
     try:
         raises()
-    except Exception as exc:
-        x = 1
+    except Exception:
+        pass
 
 test_raise.events = [(0, 'call'),
                      (1, 'line'),
@@ -191,7 +191,7 @@ def _settrace_and_raise(tracefunc):
 def settrace_and_raise(tracefunc):
     try:
         _settrace_and_raise(tracefunc)
-    except RuntimeError as exc:
+    except RuntimeError:
         pass
 
 settrace_and_raise.events = [(2, 'exception'),
diff --git a/Lib/test/test_time.py b/Lib/test/test_time.py
index 8d8d31e..80e43fa 100644
--- a/Lib/test/test_time.py
+++ b/Lib/test/test_time.py
@@ -825,7 +825,7 @@ class CPyTimeTestCase:
                     try:
                         result = pytime_converter(value, time_rnd)
                         expected = expected_func(value)
-                    except Exception as exc:
+                    except Exception:
                         self.fail("Error on timestamp conversion: %s" % debug_info)
                     self.assertEqual(result,
                                      expected,
diff --git a/Lib/test/test_traceback.py b/Lib/test/test_traceback.py
index 72dc7af..7135d99 100644
--- a/Lib/test/test_traceback.py
+++ b/Lib/test/test_traceback.py
@@ -313,7 +313,7 @@ class TracebackFormatTests(unittest.TestCase):
         with captured_output("stderr") as stderr_f:
             try:
                 f()
-            except RecursionError as exc:
+            except RecursionError:
                 render_exc()
             else:
                 self.fail("no recursion occurred")
@@ -360,7 +360,7 @@ class TracebackFormatTests(unittest.TestCase):
         with captured_output("stderr") as stderr_g:
             try:
                 g()
-            except ValueError as exc:
+            except ValueError:
                 render_exc()
             else:
                 self.fail("no value error was raised")
@@ -396,7 +396,7 @@ class TracebackFormatTests(unittest.TestCase):
         with captured_output("stderr") as stderr_h:
             try:
                 h()
-            except ValueError as exc:
+            except ValueError:
                 render_exc()
             else:
                 self.fail("no value error was raised")
@@ -424,7 +424,7 @@ class TracebackFormatTests(unittest.TestCase):
         with captured_output("stderr") as stderr_g:
             try:
                 g(traceback._RECURSIVE_CUTOFF)
-            except ValueError as exc:
+            except ValueError:
                 render_exc()
             else:
                 self.fail("no error raised")
@@ -452,7 +452,7 @@ class TracebackFormatTests(unittest.TestCase):
         with captured_output("stderr") as stderr_g:
             try:
                 g(traceback._RECURSIVE_CUTOFF + 1)
-            except ValueError as exc:
+            except ValueError:
                 render_exc()
             else:
                 self.fail("no error raised")
diff --git a/Lib/test/test_urllib2net.py b/Lib/test/test_urllib2net.py
index 040a2ce..bb0500e 100644
--- a/Lib/test/test_urllib2net.py
+++ b/Lib/test/test_urllib2net.py
@@ -199,7 +199,7 @@ class OtherNetworkTests(unittest.TestCase):
             try:
                 with urllib.request.urlopen(URL) as res:
                     pass
-            except ValueError as e:
+            except ValueError:
                 self.fail("urlopen failed for site not sending \
                            Connection:close")
             else:
diff --git a/Lib/test/test_uuid.py b/Lib/test/test_uuid.py
index ddf7e6d..b76c60e 100644
--- a/Lib/test/test_uuid.py
+++ b/Lib/test/test_uuid.py
@@ -471,7 +471,7 @@ class BaseTestUUID:
         # the value from too_large_getter above.
         try:
             self.uuid.uuid1(node=node)
-        except ValueError as e:
+        except ValueError:
             self.fail('uuid1 was given an invalid node ID')
 
     def test_uuid1(self):
diff --git a/Lib/unittest/case.py b/Lib/unittest/case.py
index bac9789..fa64a6e 100644
--- a/Lib/unittest/case.py
+++ b/Lib/unittest/case.py
@@ -712,7 +712,7 @@ class TestCase(object):
             function, args, kwargs = cls._class_cleanups.pop()
             try:
                 function(*args, **kwargs)
-            except Exception as exc:
+            except Exception:
                 cls.tearDown_exceptions.append(sys.exc_info())
 
     def __call__(self, *args, **kwds):
diff --git a/Lib/urllib/request.py b/Lib/urllib/request.py
index 721c152..ebc4118 100644
--- a/Lib/urllib/request.py
+++ b/Lib/urllib/request.py
@@ -1778,7 +1778,7 @@ class URLopener:
                 hdrs = fp.info()
                 fp.close()
                 return url2pathname(_splithost(url1)[1]), hdrs
-            except OSError as msg:
+            except OSError:
                 pass
         fp = self.open(url, data)
         try:
diff --git a/Lib/xml/sax/__init__.py b/Lib/xml/sax/__init__.py
index a0f5d40..17b7587 100644
--- a/Lib/xml/sax/__init__.py
+++ b/Lib/xml/sax/__init__.py
@@ -78,7 +78,7 @@ def make_parser(parser_list=()):
     for parser_name in list(parser_list) + default_parser_list:
         try:
             return _create_parser(parser_name)
-        except ImportError as e:
+        except ImportError:
             import sys
             if parser_name in sys.modules:
                 # The parser module was found, but importing it