This is an instance of the problems identified in Issue21882, namely that test___all__ is importing turtledemo modules and some of them have bad side effects. In this case, it's turtledemo.clock which is calling mode() which now unconditionally attempts to create a Tk window during the import. That means Tk is being called without being subject to the checks of test_support.requires('gui'). One of the reasons for having that check is to prevent this kind of crash (as documented in Issue8716) in Tk when Tk is invoked in a process that cannot make a window manager connection, as when running under a buildbot with a user name that is not logged in as the main gui user.  Note also that when Tk crashes, there is nothing the Python code can really do to recover from it.  The solution is as outlined in #21882: don't unconditionally call mode() in the import path.