Python 3: use six.iteritems() instead of iteritems()

six.iteritems() replaces dictionary.iteritems() on Python 2 and
dictionary.items() on Python 3.

Change-Id: Ie5efa65c0a992e8136087a7b78ab8e8ce967326e
Merge "Python 3: use six.iteritems() instead of iteritems()"