cause GUI tests to segfault in Cocoa Tk when run under regrtest -j
(multiple threads running subprocesses).

Patch by Diana Clarke.

test_support._is_gui_available is now defined the same way on every
platform, and now includes the Windows-specific check that had been in the
Windows version of _is_gui_available and the OSX-specific check that was
in tkinter.test.support.check_tk_availability.  Also, every platform
checks whether Tk can be instantiated (if the platform-specific checks
passed).

supported by Doc/Makefile, as well as a bit of modernization,
cleanup, and notes about the difference between Unix and Windows.

Issue #21321: itertools.islice() now releases the reference to the source iterator when the slice is exhausted.

Patch by Anton Afanasyev.

Issue #9815: assertRaises now tries to clear references to local variables in the exception's traceback.

Patch by Claudiu Popa.

Patch by Diana Clarke.

Pointed out by Brian Kearns.

This should stop Buildbot from falsely reporting a warning on Windows bots.

children.

may be calling wait() or poll() on a Popen instance at the same time
without losing the Popen.returncode value.  Fixes issue #21291.

Issue #21127: Path objects can now be instantiated from str subclass instances (such as numpy.str_).

Thanks to Antony Lee for the report and preliminary patch.

reformat width in the configuration menu.

facility. Provides a better way to handle file descriptor close.

Address issue #15002 . Patch contributed by Christian Theune.

Fix by 'amathew', test by Marek Stepniowski.

when launched on OS X.  (Original patch by Ronald Oussoren)