The only thing I still see is a pair of ThemeChanged warnings from 2.7.  Using binary search, I identified test_editmenu as the culprit.  This in spite of all the cleanup I can think of

    @classmethod
    def tearDownClass(cls):
        del cls.text, cls.entry, cls.spin
        cls.root.clipboard_clear()
        cls.root.update_idletasks()
        cls.root.update()
        cls.root.destroy()
        del cls.root

When I tried to determine which test method(s) gave the warning, as disable all to make sure the warnings vanished, which then did.  But after re-enabling, the warnings did not come back -- until they did after a few more runs.  I suspect that the only permanent solution will be Serhiy's patch to have .destroy cancel pending callbacks.