Remove six Replace the following items with Python 3 style code.
- six.moves
- six.StringIO
- six.add_metaclass
- six.string_types
- six.binary_type
- six.text_type
- six.integer_types
- six.PY3
- six.PY2
- six.iterkeys

Change-Id: Id9f2076be1a6a2d99db5acb682df8bebe893de36