--- a/mercurial/error.py	Mon Apr 21 16:02:03 2014 -0700
+++ b/mercurial/error.py	Mon Apr 21 18:59:09 2014 -0700
@@ -94,3 +94,7 @@
 
 class SignatureError(Exception):
     pass
+
+class PushRaced(RuntimeError):
+    """An exception raised during unbundling that indicate a push race"""
+