py3: drop b'' while formatting ResponseError

contrib/python3-whitelist

@@ -36,6 +36,7 b' test-bundle-r.t'
 test-bundle-type.t
 test-bundle-vs-outgoing.t
 test-bundle.t
+test-bundle2-exchange.t
 test-bundle2-multiple-changegroups.t
 test-bundle2-pushback.t
 test-cappedreader.py

mercurial/scmutil.py

@@ -201,7 +201,7 b' def callcatch(ui, func):'
         elif not msg:
             ui.warn(_(" empty string\n"))
         else:
-            ui.warn("\n%r\n" % stringutil.ellipsis(msg))
+            ui.warn("\n%r\n" % pycompat.bytestr(stringutil.ellipsis(msg)))
     except error.CensoredNodeError as inst:
         ui.warn(_("abort: file censored %s!\n") % inst)
     except error.RevlogError as inst: