Fix unicode errors with bzrlib.

bzrlib is even more janky than I thought with regards to its treatment of
strings--it expects repository locators to be str objects with ascii encoding.
This means, I believe, that if you had a unicode path on your filesystem, you
couldn't have a bazaar repository in that path.

Encode all the things before passing them into bzrlib.

Testing done:
Ran unit tests. Some bzr things are failing for other (configuration/setup)
reasons but there are no more unicode/string errors.

Reviewed at https://reviews.reviewboard.org/r/4993/