py3: add a b'' prefix in tests/test-remotefilelog-pull-noshallow.t
This makes the test pass on Python 3.
# skip-blame because just b'' prefix.
Differential Revision: https://phab.mercurial-scm.org/D5427
error: implement __str__ on RevlogError to fix some output defects on Py3
We open-code encoding.unimethod here to avoid cycles, and do a local
import of encoding when someone str()s a RevlogError. It's not my
favorite solution, but it gets the job done.
Differential Revision: https://phab.mercurial-scm.org/D5426