mock_open()().readline() fails at EOF

Using mock (2.0.0), I fell foul of issue 26907. The same fix applied by hand fixes it.

In [1]: import mock

In [2]: o = mock.mock_open(read_data="fred")

In [3]: f = o()

In [4]: f.readline()
Out[4]: 'fred'

In [5]: f.readline()
---------------------------------------------------------------------------
StopIteration                             Traceback (most recent call last)
<ipython-input-5-c4ba08551b5f> in <module>()
----> 1 f.readline()

/home/usr/.virtualenvs/dtree/lib/python2.7/site-packages/mock/mock.py in __call__(_mock_self, *args, **kwargs)
   1060         # in the signature
   1061         _mock_self._mock_check_sig(*args, **kwargs)
-> 1062         return _mock_self._mock_call(*args, **kwargs)
   1063
   1064

/home/usr/.virtualenvs/dtree/lib/python2.7/site-packages/mock/mock.py in _mock_call(_mock_self, *args, **kwargs)
   1119
   1120             if not _callable(effect):
-> 1121                 result = next(effect)
   1122                 if _is_exception(result):
   1123                     raise result

/home//.virtualenvs/dtree/lib/python2.7/site-packages/mock/mock.py in next(obj, _next)
    107         if getattr(obj, '__next__', None):
    108             return obj.__next__()
--> 109         return _next(obj)
    110
    111     del _next

StopIteration:

[cjw296]

Yay! Now in the backport: 1a19afa054c22264e0c53b78e19ee453921aca9c

[rbtcollins]

ok, we need to do another backporting run,