Python 3 compatability

* use six.iteritems()
* replace basestring with six.string_types
* convert print statements to functions (they're all debugging and should
  be removed eventually anyway)

Change-Id: Icb14212bcb408e63816bfec3922a697bc1a6c946
Merge branch 'volume-keystone' into dt-test
Merge branch 'identity-catalog' into dt-test
Merge branch 'py33' into dt-test