diff -r 3d14c1217117 -r 0ca8410ea345 mercurial/ancestor.py
--- a/mercurial/ancestor.py	Sat May 16 09:03:21 2015 +0200
+++ b/mercurial/ancestor.py	Sat May 16 11:28:04 2015 -0700
@@ -5,8 +5,8 @@
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
+import collections
 import heapq
-import util
 from node import nullrev
 
 def commonancestorsheads(pfunc, *nodes):
@@ -314,7 +314,7 @@
 
         parentrevs = self._parentrevs
         stoprev = self._stoprev
-        visit = util.deque(revs)
+        visit = collections.deque(revs)
 
         while visit:
             for parent in parentrevs(visit.popleft()):