Issue #19940: ssl.cert_time_to_seconds() now interprets the given time string in the UTC timezone (as specified in RFC 5280), not the local timezone.

Patch by Akira.
Issue #21312: Update the thread_foobar.h template file to include newer threading APIs.  Patch by Jack McCracken.
Issue #17861: Allow generate_opcode_h to run with a system Python 2.5.
Patch by David Bolen.
Issue #20355: -W command line options now have higher priority than the PYTHONWARNINGS environment variable.  Patch by Arfrever.
Remove a workaround for fixed issue #20355.
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 #9307: document the various Py_TPFLAGS_*_SUBCLASS flags.  Patch by Yury V. Zaytsev.
Issue #9307: document the various Py_TPFLAGS_*_SUBCLASS flags.  Patch by Yury V. Zaytsev.
Issue #18727: improve test coverage of the csv module by testing for DictWriter.writerows.
Patch by Muhammad Jehanzeb.
fix isuse #13248: remove previously deprecated asyncore.dispatcher __getattr__ cheap inheritance hack.
merge heads
Issue #21026: Augment site doc based on experiments. Patch by Carol Willing.
Merge with 3.4
Closes 21048: Index 'as' in import and with statements.
Merge with 3.4
Issue #21055: Index (augmented) assignment symbols.
Merge with 3.4