def test_formatSystemUnformattable(self):
        """
        System is not supplanted by namespace and level.
        """
        event = dict(log_format=u"XYZZY", log_system=Unformattable())
        self.assertEqual(
            formatEventAsClassicLogText(event),
            u"- [UNFORMATTABLE] XYZZY\n",
        )

        System is not supplanted by namespace and level.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/logger/test/test_format.py