BUG: register path issues with binary and unicode strings

[hannesdelbeke]

while adding path support to pyblish, i noticed some paths change in unpredictable ways
original thread #377

starting a new issue here to discuss this.

u"c:\some\special\södär\testpath".encode('utf-8') -> binary

b'c:\some\special\s\xc3\xb6d\xc3\xa4r\testpath' becomes
b'c:\\some\\special\\s\xc3\xb6d\xc3\xa4r\testpath' when added to registered paths using pyblish.plugin.register_plugin_path(path)
notice the \ before testpath is a single one, but all other folder \ are 2 now

b'c:\bytes\are\cool' becomes
b'c:\\bytes\\are\\cool'

[hannesdelbeke]

curious if this relates too https://docs.python.org/3/whatsnew/3.0.html#text-vs-data-instead-of-unicode-vs-8-bit