I noticed an issue passing in unicode to os.path.relpath.

Specifically that in some cases when passing in unicode I would get back unicode and others I would get back a string. Below I demonstrate the issue. I also attached a patch.

Is this an issue or am I misunderstanding something. Is the patch reasonable? Totally willing to improve and i'll admit I cannot test the ntpath version.

Python 2.7.6 (default, Apr  9 2014, 11:48:52)
[GCC 4.2.1 Compatible Apple LLVM 5.1 (clang-503.0.38)] on darwin
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>>> import os
>>> os.path.relpath(u'.', u'.')
'.'
>>> os.path.relpath(u'.', u'../')
u'bachmann'