>>> with mock.patch('__main__.foo', side_effect=[1,Exception()]) as f:
...     f(1)
...     f(2)
...
1
Traceback (most recent call last):
  File "<stdin>", line 3, in <module>
  File "/home/dan/nova/.tox/py27/lib/python2.7/site-packages/mock/mock.py", line 1092, in __call__
    return _mock_self._mock_call(*args, **kwargs)
  File "/home/dan/nova/.tox/py27/lib/python2.7/site-packages/mock/mock.py", line 1147, in _mock_call
    raise result
Exception