Error parsing __all__ when opening parenthesis is on line by itself.

[jkrukoff]

With the following test file:

__all__ = (
    'a',
    'b',
    'c',
)


def a():
    pass


def b():
    pass


def c():
    pass

pep257 version 0.3.2 reports that it is unable to evaluate all:

Could not evaluate contents of __all__. That means pep257 cannot decide which definitions are public. Variable __all__ should be present at most once in each file, in form `__all__ = ('a_public_function', 'APublicClass', ...)`. More info on __all__: http://stackoverflow.com/q/44834/. 

If I reformat all to include something on the opening line, pep257 is able to continue:

__all__ = ('a',
    'b',
    'c',
)