def test_findNoFailure(self):
        """
        Outside of an exception handler, _findFailure should return None.
        """
        if sys.version_info < (3, 0):
            sys.exc_clear()
        self.assertIsNone(sys.exc_info()[-1]) #environment sanity check
        self.assertIsNone(failure.Failure._findFailure())

        Outside of an exception handler, _findFailure should return None.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_failure.py