diff -r f00813325c5a -r 21c44c1aed87 mercurial/error.py
--- a/mercurial/error.py	Wed Oct 15 17:02:44 2014 -0700
+++ b/mercurial/error.py	Thu Oct 16 02:05:06 2014 -0700
@@ -30,6 +30,9 @@
     def __str__(self):
         return RevlogError.__str__(self)
 
+class FilteredLookupError(LookupError):
+    pass
+
 class ManifestLookupError(LookupError):
     pass