def test_twistReactorDoesntExitWithSignal(self):
        """
        _exitWithSignal is not called if the reactor's _exitSignal attribute
        is zero.
        """
        reactor = SignalCapturingMemoryReactor()
        reactor._exitSignal = None
        options = TwistOptions()
        options["reactor"] = reactor
        options["fileLogObserverFactory"] = jsonFileLogObserver

        Twist.run(options)
        self.assertFalse(self.exitWithSignalCalled)

        _exitWithSignal is not called if the reactor's _exitSignal attribute
        is zero.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/application/twist/test/test_twist.py