Issue #21377: PyBytes_Concat() now tries to concatenate in-place when the first argument has a reference count of 1.
Patch by Nikolaus Rath.

in the root of the source tree, which passes all arguments through
to the most recently built interpreter.

Decimal.quantize() method in the Python version.  It had never been
present in the C version.

Patch by Lukas Vacek.

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

Patch by Anton Afanasyev.

Issue #21057: TextIOWrapper now allows the underlying binary stream's read() or read1() method to return an arbitrary bytes-like object (such as a memoryview).

Patch by Nikolaus Rath.

Issue #20951: SSLSocket.send() now raises either SSLWantReadError or SSLWantWriteError on a non-blocking socket if the operation would block. Previously, it would return 0.

Patch by Nikolaus Rath.

fix isuse #13248: remove previously deprecated asyncore.dispatcher __getattr__ cheap inheritance hack.

Patch by Muhammad Jehanzeb.

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

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

Issue #20355: -W command line options now have higher priority than the PYTHONWARNINGS environment variable.  Patch by Arfrever.

Patch by David Bolen.

Issue #21312: Update the thread_foobar.h template file to include newer threading APIs.  Patch by Jack McCracken.