def dieNext(self):
        """
        Make the next result from my worker iterator be raising an
        L{UnhandledException}.
        """
        def ignoreUnhandled(failure):
            failure.trap(UnhandledException)
            return None
        self._doDieNext = True

        Make the next result from my worker iterator be raising an
        L{UnhandledException}.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_cooperator.py