def test_mockErrorECHILDInReapProcess(self):
        """
        Test that reapProcess doesn't log anything when waitpid raises a
        C{OSError} with errno C{ECHILD}.
        """
        self.mockos.child = False
        cmd = b'/mock/ouch'
        self.mockos.waitChild = (0, 0)

        d = defer.Deferred()
        p = TrivialProcessProtocol(d)
        proc = reactor.spawnProcess(p, cmd, [b'ouch'], env=None,
                                    usePTY=False)
        self.assertEqual(self.mockos.actions, [("fork", False), "waitpid"])

        self.mockos.raiseWaitPid = OSError()
        self.mockos.raiseWaitPid.errno = errno.ECHILD
        # This should not produce any errors
        proc.reapProcess()

        Test that reapProcess doesn't log anything when waitpid raises a
        C{OSError} with errno C{ECHILD}.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_process.py