mercurial/scmutil.py

--- a/mercurial/scmutil.py	Thu Mar 20 17:34:02 2014 -0700
+++ b/mercurial/scmutil.py	Wed Mar 19 00:18:30 2014 +0100
@@ -732,10 +732,10 @@
     missings.sort()
     if missings:
         raise error.RequirementError(
-            _("unknown repository format: requires features '%s' (upgrade "
-              "Mercurial)") % "', '".join(missings),
+            _("repository requires features unknown to this Mercurial: %s")
+            % " ".join(missings),
             hint=_("see http://mercurial.selenic.com/wiki/MissingRequirement"
-                   " for details"))
+                   " for more information"))
     return requirements
 
 class filecachesubentry(object):