diff -r ddd4996740c7 -r f1745323a567 mercurial/context.py
--- a/mercurial/context.py	Tue May 08 12:05:45 2012 -0500
+++ b/mercurial/context.py	Wed May 09 02:46:58 2012 +0300
@@ -697,7 +697,7 @@
             yield c
 
     def copies(self, c2):
-        if not util.hasattr(self, "_copycache"):
+        if not util.safehasattr(self, "_copycache"):
             self._copycache = {}
         sc2 = str(c2)
         if sc2 not in self._copycache: