test_convert_stdlib fails under Python 3.7.0

[berkerpeksag]

From https://travis-ci.org/berkerpeksag/astor/jobs/357390920:

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FAIL: test_convert_stdlib (tests.test_rtrip.RtripTestCase)
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Traceback (most recent call last):
  File "/home/travis/build/berkerpeksag/astor/tests/test_rtrip.py", line 24, in test_convert_stdlib
    self.assertEqual(result, [])
AssertionError: Lists differ: ['/home/travis/build/berkerpeksag/astor/.t[35785 chars].py'] != []
First list contains 344 additional elements.
First extra element 0:
'/home/travis/build/berkerpeksag/astor/.tox/py37/lib/python3.7/os.py'

[radomirbosak]

I would say this is partly caused by the new python 3.7 docstring attribute mentioned in #101 . There may be other problems though.

[berkerpeksag]

It looks like the only remaining problem was #101 so closing this as 'fixed'.