Related to #1966. Previously, we used a `syspath` call inside MediaFile, which
probably wasn't right: the constructor should behave like `open` in that we
need to use pass an OS path.
This was a vestige from when we used to need the unittest2 library for pre-2.7
compatibility. Now that we require Python 2.7, we aren't using that library
and this indirection wasn't doing any good.
This reverts commit 9c41c39913.
That commit used byte strings for the `if __name__ == '__main__'` pattern,
which was necessary when we were doing unicode_literals. But it is wrong on
Python 3, and now that we're liberated from unicode_literals, we need to go
back to native strings for this comparison.
Include import of __future__ features division, absolute_imports and
print_function everywhere. Don't add unicode_literals yet for it is
harder to convert.
Goal is smoothing the transition to python 3.
Uses the new API from the previous commit and fixes#963.
There is a possible issue with backwards compatibility: Changes to the
item in the 'write' event do not propagate to the tags anymore. But I'm
not aware of other plugins that use the API in that way.
