--- a/mercurial/dagparser.py	Mon May 18 12:18:00 2015 -0500
+++ b/mercurial/dagparser.py	Mon May 18 12:22:44 2015 -0500
@@ -176,10 +176,7 @@
     chiter = (c for c in desc)
 
     def nextch():
-        try:
-            return chiter.next()
-        except StopIteration:
-            return '\0'
+        return next(chiter, '\0')
 
     def nextrun(c, allow):
         s = ''