py3: add b'' prefix in test-mq-qrefresh-replace-log-message.t

# ski-blame as we just added b''

Differential Revision: https://phab.mercurial-scm.org/D2322

tests/test-mq-qrefresh-replace-log-message.t

@@ -119,7 +119,7 b' Test saving last-message.txt:'
   > def reposetup(ui, repo):
   >     class commitfailure(repo.__class__):
   >         def commit(self, *args, **kwargs):
-  >             raise error.Abort('emulating unexpected abort')
+  >             raise error.Abort(b'emulating unexpected abort')
   >     repo.__class__ = commitfailure
   > EOF