def test_outputWithErrorIgnored(self):
        """
        The L{Deferred} returned by L{getProcessOutput} is fired with an
        L{IOError} L{Failure} if the child process writes to stderr.
        """
        # make sure stderr raises an error normally
        scriptFile = self.makeSourceFile([
            'import sys',
            'sys.stderr.write("hello world\\n")'
            ])

        d = utils.getProcessOutput(self.exe, ['-u', scriptFile])
        d = self.assertFailure(d, IOError)
        def cbFailed(err):
            return self.assertFailure(err.processEnded, error.ProcessDone)
        d.addCallback(cbFailed)
        return d

        The L{Deferred} returned by L{getProcessOutput} is fired with an
        L{IOError} L{Failure} if the child process writes to stderr.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_iutils.py