context: fix %-formatting on Python 3

changeid could be an int or a bytestr, so use our pycompat wrapper.

Differential Revision: https://phab.mercurial-scm.org/D3585

mercurial/context.py

@@ -432,7 +432,7 b' class changectx(basectx):'
             # lookup failed
         except (error.FilteredIndexError, error.FilteredLookupError):
             raise error.FilteredRepoLookupError(_("filtered revision '%s'")
-                                                % changeid)
+                                                % pycompat.bytestr(changeid))
         except error.FilteredRepoLookupError:
             raise
         except IndexError: