diff -r f5a1aa8c6987 -r 5046c906b25d mercurial/dispatch.py
--- a/mercurial/dispatch.py	Fri May 11 10:36:28 2018 -0700
+++ b/mercurial/dispatch.py	Fri Apr 27 21:55:02 2018 +0530
@@ -1028,7 +1028,7 @@
                      '** which supports versions %s of Mercurial.\n'
                      '** Please disable %s and try your action again.\n'
                      '** If that fixes the bug please report it to %s\n')
-                   % (name, testedwith, name, report))
+                   % (name, testedwith, name, stringutil.forcebytestr(report)))
     else:
         bugtracker = ui.config('ui', 'supportcontact')
         if bugtracker is None: