Revert "bpo-29406: asyncio SSL contexts leak sockets after calling close with certain servers (#409)" (#2111)

This reverts commit a608d2d5.

The depth argument limits recursion.

SSLObject has recv() and send(), but they don't do any network io.

Also fixed a few more line endings that were missed in GH-840, which were causing failure.

- new PYTHONCOERCECLOCALE config setting
- coerces legacy C locale to C.UTF-8, C.utf8 or UTF-8 by default
- always uses C.UTF-8 on Android
- uses `surrogateescape` on stdin and stdout in the coercion
  target locales
- configure option to disable locale coercion at build time
- configure option to disable C locale warning at build time

#30624 / selectors: use bare except clause in order to not leave the fd in a bad state in case of error (#2082)

Updates checked-in line endings on several files.

This PR contains two updates to typing module:

- Support ContextManager on all versions (original PR by Jelle Zijlstra).
- Add generic AsyncContextManager.

Mock os.register_at_fork() when importing the random module, since
this function doesn't allow to unregister callbacks and so leaked
memory.

multiprocessing.Queue.get() with a timeout now polls its reader in
non-blocking mode if it succeeded to aquire the lock but the acquire
took longer than the timeout.
Co-Authored-By: Grzegorz Grzywacz <grzgrzgrz3@gmail.com>

Running our unit tests with `-bb` enabled triggered this failure.

The function '_PyArg_ParseStack()' and
'_PyArg_UnpackStack' were failing (with error
"XXX() takes Y argument (Z given)") before
the function '_PyArg_NoStackKeywords()' was called.
Thus, the latter did not raise its more meaningful
error : "XXX() takes no keyword arguments".

Mention that fnmatchcase does not call normcase, and fnmatch does.

* asyncio SSL contexts leak sockets after calling close with certain servers

* cleanup _shutdown_timeout_handle on _fatal_error

This will allow for centralized management of the Codecov config to prevent skew as well as easier management going forward.

Closes python/core-workflow#81.

Document that assertNotRegexpMatches is a deprecated alias for assertNotRegex.

* #30014: make selectors.DefaultSelector.modify() faster by relying on selector's modify() method instead of un/register()ing the fd

* #30014: add unit test

* speedup poll/epoll/devpoll modify() method by using internal modify() call

* update doc

* address PR comments

* update NEWS entries

* use != instead of 'is not'

Avoid a deadlock when the waiter who is about to take the lock is
cancelled

Issue #27585

* Fix regression in error message introduced in bpo-29951.

* Add test.

* Make the test more strong.

contextlib.AbstractContextManager now supports anti-registration
by setting __enter__ = None or __exit__ = None, following the pattern
introduced in bpo-25958.

Test C functions:

* _PyObject_FastCall()
* _PyObject_FastCallDict()
* _PyObject_FastCallKeywords()

* RFC 1750 has been been obsoleted by RFC 4086.
* RFC 3280 has been obsoleted by RFC 5280.
* RFC 4366 has been obsoleted by RFC 6066.

See discussion:
  https://github.com/python/cpython/pull/1992#issuecomment-307024778

* Add a new option taking a filename to get a list of test names to
  filter tests.
* support.match_tests becomes a list.
* Modify run_unittest() to accept to match the whole test identifier,
  not just a part of a test identifier.

For example, the following command only runs test_default_timeout()
of the BarrierTests class of test_threading:

$ ./python -m test -v test_threading -m test.test_threading.BarrierTests.test_default_timeout

Remove also some empty lines from test_regrtest.py to make flake8
tool happy.