Don't unset and set againt the HAVE_CLOCK define, reorder the #if tests
instead. Fix also the definition of the timezone encoding.

Windows if the mbcs codec is not available, and fail with a fatal error if we
cannot get the locale encoding (if nl_langinfo(CODESET) is not available)
instead of using UTF-8.

Python 3.3 has the correct fix for #12429, use pthread_sigmask().

On FreeBSD, the SIGALRM signal is sometimes received by the reader thread.

test_tk or test_ttk_guionly under a username that is not currently logged
in to the console windowserver (as may be the case under buildbot or ssh).

test_tk or test_ttk_guionly under a username that is not currently logged
in to the console windowserver (as may be the case under buildbot or ssh).

emitted at shutdown, if globals()['__file__'] is None.

shutdown, if globals()['__file__'] is None.

binary mode, instead of text mode using the locale encoding, to avoid encoding
issues.

instead of text mode using the locale encoding, to avoid encoding issues.

binary mode, instead of text mode using the locale encoding, to support other
encodings than UTF-8 (scripts using the coding cookie).

instead of text mode using the locale encoding, to support other encodings than
UTF-8 (scripts using the coding cookie).

mode instead of the text mode (using the locale encoding) to avoid encoding
issues.

of the text mode (using the locale encoding) to avoid encoding issues.

This requires some trickery to properly save the exception state if the
generator creates its own exception state.

This prevents generator exception state from leaking into the caller.

Closes #12475.