def test_asynchronousError(self):
        """
        Like L{test_asynchronousException}, but for a method which returns a
        Deferred failing with an L{pb.Error} subclass.
        """
        return self._exceptionTest(
            'asynchronousError', AsynchronousError, False)

        Like L{test_asynchronousException}, but for a method which returns a
        Deferred failing with an L{pb.Error} subclass.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/spread/test/test_pbfailure.py