diff -r 82e0b12054a8 -r ba86b1bdbcab entity.py
--- a/entity.py	Thu Aug 27 20:22:51 2009 +0200
+++ b/entity.py	Fri Aug 28 14:15:00 2009 +0200
@@ -315,7 +315,7 @@
     def __hash__(self):
         return id(self)
 
-    def __cmp__(self):
+    def __cmp__(self, other):
         raise NotImplementedError('comparison not implemented for %s' % self.__class__)
 
     def pre_add_hook(self):