diff -r 94afe7bc87a9 -r 99eee847beaa mercurial/windows.py
--- a/mercurial/windows.py	Sun May 09 22:51:25 2010 +0200
+++ b/mercurial/windows.py	Mon May 10 21:09:48 2010 +0200
@@ -363,6 +363,10 @@
     # current line but on the new one. Keep room for it.
     return 79
 
+def groupmembers(name):
+    # Don't support groups on Windows for now
+    raise KeyError()
+
 try:
     # override functions with win32 versions if possible
     from win32 import *