Adding iteritems validation

Since in Python 3 there's no longer dict.iteritems()
and to keep the compatibility with Python 2, instead of call
dict.iteritems(), we must call six.iteritems(dict).
This patch is to avoid broken this compatibility in the future
adding a validation for iteritems.

Change-Id: I7c5e312801db886483b0ff5c45a80cba6848c95e
Merge "Adding iteritems validation"