Issue #2670: urllib2.build_opener() failed when two handlers
derive the same default base class.

Backport of r62463.
diff --git a/Misc/NEWS b/Misc/NEWS
index b9ce278..d66e26c 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -45,6 +45,9 @@
 Library
 -------
 
+- Issue #2670:  Fix a failure in urllib2.build_opener(), when passed two
+  handlers that derive the same default base class.
+
 - Issue #2495: tokenize.untokenize now inserts a space between two consecutive
   string literals; previously, ["" ""] was rendered as [""""], which is
   incorrect python code.