--- a/server/hooks.py	Tue Aug 18 15:50:46 2009 +0200
+++ b/server/hooks.py	Tue Aug 18 16:05:50 2009 +0200
@@ -430,7 +430,9 @@
             try:
                 iter(state.transitions(entity, toeid)).next()
             except StopIteration:
-                msg = session._('transition is not allowed')
+                _ = session._
+                msg = _('transition from %s to %s does not exist or is not allowed') % (
+                    _(state.name), _(session.entity_from_eid(toeid).name))
                 raise ValidationError(fromeid, {'in_state': msg})
         else:
             # not a transition