--- a/mercurial/util.py	Fri Jun 03 21:49:26 2016 +0900
+++ b/mercurial/util.py	Sat Jun 04 14:38:00 2016 +0530
@@ -47,6 +47,7 @@
 
 for attr in (
     'empty',
+    'pickle',
     'queue',
     'urlerr',
     # we do import urlreq, but we do it outside the loop