py3: avoid using %r format on bytes
Before the patch, the 'b' prefix appeared in the formatted string. Wrapping the
bytes as pycompat.bytestr solves this problem.
Eventually, I think that we should move away from using %r (like 975e517451a6
and 4d6019c0e0ef did), but that would change output of non-ASCII bytes on
Python 2, so we can’t do it on the stable branch. Also, many places continue to
use %r, so it would be a good idea to do the change all at once.
(binary:application/octet-stream)