py3: use pycompat.bytestr() on bytes before %r-ing it

Differential Revision: https://phab.mercurial-scm.org/D3567

mercurial/match.py

@@ -404,7 +404,7 b' class patternmatcher(basematcher):'
 
     @encoding.strmethod
     def __repr__(self):
-        return ('<patternmatcher patterns=%r>' % self._pats)
+        return ('<patternmatcher patterns=%r>' % pycompat.bytestr(self._pats))
 
 class includematcher(basematcher):