diff -r 7293cb91bf2a -r 430a10669928 mercurial/commands.py
--- a/mercurial/commands.py	Sun Jun 26 14:14:04 2005 +0100
+++ b/mercurial/commands.py	Sun Jun 26 14:14:52 2005 +0100
@@ -340,7 +340,7 @@
         revs = map(lambda x: repo.lookup(x), opts['rev'])
 
     if len(revs) > 2:
-        self.ui.warn("too many revisions to diff\n")
+        ui.warn("too many revisions to diff\n")
         sys.exit(1)
 
     if files: