diff -r f5983805574e -r ead25aa27a43 mercurial/ancestor.py
--- a/mercurial/ancestor.py	Mon May 16 21:30:32 2016 +0000
+++ b/mercurial/ancestor.py	Mon May 16 21:30:53 2016 +0000
@@ -291,7 +291,7 @@
     def __nonzero__(self):
         """False if the set is empty, True otherwise."""
         try:
-            iter(self).next()
+            next(iter(self))
             return True
         except StopIteration:
             return False