我继承的单元测试现在失败

 p = subprocess.Popen(command,shell=True,stdout=subprocess.PIPE)
 logging.warning('Not hitting here.')

回溯

File "/usr1/tsmith/miniconda3/lib/python3.7/unittest/mock.py",line 960,in __call__
    return _mock_self._mock_call(*args,**kwargs)
  File "/usr1/tsmith/miniconda3/lib/python3.7/unittest/mock.py",line 1022,in _mock_call
    result = next(effect)
StopIteration`

有什么想法要对此进行调查吗？