Patch# 1258 by Christian Heimes: kill basestring.
I like this because it makes the code shorter! :-)
diff --git a/Lib/email/iterators.py b/Lib/email/iterators.py
index e4476e3..3adc4a0 100644
--- a/Lib/email/iterators.py
+++ b/Lib/email/iterators.py
@@ -39,7 +39,7 @@
     """
     for subpart in msg.walk():
         payload = subpart.get_payload(decode=decode)
-        if isinstance(payload, basestring):
+        if isinstance(payload, str):
             for line in StringIO(payload):
                 yield line