Issue #18676: Change 'positive' to 'non-negative' in queue.py put and get
docstrings and ValueError messages. Patch by Zhongyue Luo
Fix refcounting issue with extension types in tkinter.
(issue #15721)
Issue #18676: Merge from 3.3
Issue #10241: Clear extension module dict copies at interpreter shutdown.
Patch by Neil Schemenauer, minimally modified.

(re-apply after fix for tkinter-related crash)
Merge heads
Merge
Issue #15301: skip new test method so Windows builtbots stop failing.
#18663: document that assertAlmostEqual also works when the values are equal and add tests.
#18663: merge with 3.3.
Issue #18706: Fix a test for issue #18681 so it no longer breaks test_codeccallbacks*.
Issue #18706: Fix a test for issue #18681 so it no longer breaks test_codeccallbacks*.