Use functools.reduce() in difflib instead of __builtin__.reduce() to silence
warnings when running under -3.
diff --git a/Lib/difflib.py b/Lib/difflib.py
index 63b42e9..7498e6f 100644
--- a/Lib/difflib.py
+++ b/Lib/difflib.py
@@ -34,6 +34,7 @@
 
 import heapq
 from collections import namedtuple as _namedtuple
+from functools import reduce
 
 Match = _namedtuple('Match', 'a b size')