def test_clearIgnores(self):
        """
        Check that C{_clearIgnores} ensures that previously ignored errors
        get captured.
        """
        self.observer._ignoreErrors(ZeroDivisionError)
        self.observer._clearIgnores()
        f = makeFailure()
        self.observer.gotEvent({'message': (),
                                'time': time.time(), 'isError': 1,
                                'system': '-', 'failure': f,
                                'why': None})
        self.assertEqual(self.observer.getErrors(), [f])

        Check that C{_clearIgnores} ensures that previously ignored errors
        get captured.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/trial/test/test_log.py