--- a/mercurial/ui.py	Fri Dec 05 22:22:14 2008 +0100
+++ b/mercurial/ui.py	Sat Dec 06 14:27:31 2008 +0100
@@ -350,7 +350,7 @@
         if not user:
             raise util.Abort(_("Please specify a username."))
         if "\n" in user:
-            raise util.Abort(_("username %s contains a newline\n") % `user`)
+            raise util.Abort(_("username %s contains a newline\n") % repr(user))
         return user
 
     def shortuser(self, user):