Convert input to a string object. Fixes #909230.

Backported 2.3.

Lib/encodings/idna.py

@@ -171,6 +171,7 @@ class Codec(codecs.Codec):
             labels = dots.split(input)
         else:
             # Must be ASCII string
+            input = str(input)
             unicode(input, "ascii")
             labels = input.split(".")