diff -r a48ad118c558 -r dfd009e5f9f2 mercurial/dagparser.py
--- a/mercurial/dagparser.py	Sun Sep 03 15:28:39 2017 +0900
+++ b/mercurial/dagparser.py	Sun Sep 03 15:32:45 2017 +0900
@@ -181,7 +181,7 @@
         else:
             return labels[ref]
 
-    chiter = (c for c in desc)
+    chiter = pycompat.iterbytestr(desc)
 
     def nextch():
         return next(chiter, '\0')