def test_eventAsTextSystemMissing(self):
        """
        If includeSystem is specified with a missing system [-#-]
        is used.
        """
        try:
            raise CapturedError("This is a fake error")
        except CapturedError:
            f = Failure()

        t = mktime((2013, 9, 24, 11, 40, 47, 1, 267, 1))
        event = {
            "log_format": u"ABCD",
            "log_time": t,
        }
        event["log_failure"] = f
        eventText = eventAsText(
            event,
            includeTimestamp=False,
            includeTraceback=False,
            includeSystem=True,
        )
        self.assertEqual(
            eventText,
            u"[-\x23-] ABCD",
        )

        If includeSystem is specified with a missing system [-#-]
        is used.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/logger/test/test_format.py