Issue #16903: Popen.communicate() on Unix now accepts strings when
universal_newlines is true as on Windows.
Fix test_tools hangs on Windows. Patch by Jeremy Kloth.
#17091: update docstring for _thread.Lock.acquire.

The main docs were fixed to remove mention of None long ago,
but the docstring was not.  Reported by Armin Rigo, patch
by Ian Cordasco.
Issue #17089: Expat parser now correctly works with string input not only when
an internal XML encoding is UTF-8 or US-ASCII.  It now accepts bytes and
strings larger than 2 GiB.