convert-bazaar: use breezy package instead of old bzr one Breezy is the most recent of the two, and works on Python 3 while being compatible with the (old) Bazaar file format. This patch contains a variety of unicode <-> bytes changes, API breakage fixing, restoring failing imports and changing the executable from `bzr` to `brz`. I recommend using the debian packages for `brz` and `python3-breezy` (3.1+), because the pip package seems to be haunted by radioactive dragons. Differential Revision: https://phab.mercurial-scm.org/D10513