Issue #17860: explicitly mention that std* streams are opened in binary mode by default.

The documentation does mention that the streams are opened in text mode
when univeral_newlines is true, but not that that they are opened in
binary mode when that argument is false and that seems to confuse at
least some users.
Issue #18375: Assume --randomize when --randseed is used for running the testsuite.
Issue #12990: The "Python Launcher" on OSX could not launch python scripts that have paths that include wide characters.
test_ftplib: silence a BytesWarning when checking TypeError
#18380: pass regex flags to the right argument.  Patch by Valentina Mukhamedzhanova.
Issue #18351: Fix various issues with
importlib._bootstrap._get_sourcefile().

Thanks to its only use by the C API, it was never properly tested
until now.

Thanks to Neal Norwitz for discovering the bug and Madison May for the patch.