Use six.iteritems to make dict work on Python2/3

six.iteritems returns an iterator over dictionary‘s items.
This replaces dictionary.iteritems() on Python 2 and dictionary.items()
on Python 3. See http://pythonhosted.org/six/#six.iteritems

Part of blueprint py33
Change-Id: I72ef4e2ab6944e58069f9476b2e6dca10c9c94aa
Merge "Use six.iteritems to make dict work on Python2/3"