The tests now pass all combinations of -O/-OO and -B.  See also #7071
and #6292 for previous variations on the same theme.

test_versionpredicate needs a skip when sys.flags.optimize is true, but
I don’t know how to make that work with a DocTestSuite.

returns None.

an IOError if the file is closed.

the file is closed.

Tools/msi/msi.py

correctly references to "bogus variable" (e.g. "prefix=$/opt/python").

each call to their encode() method anymore, but continue to call the reset()
method if the final argument is True.

their encode() method anymore, but continue to call the reset() method if the
final argument is True.