def test_stderr(self):
        """
        ProcessProtocol.transport.closeStderr actually closes the pipe.
        """
        d = self.doit(2)
        def _check(errput):
            # there should be no stderr open, so nothing for it to
            # write the error to.
            self.assertEqual(errput, b'')
        d.addCallback(_check)
        return d

        ProcessProtocol.transport.closeStderr actually closes the pipe.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_process.py