iso8601 is required by default on keystone

It seems that the module iso8601 is now needed by default on keystone, it is only included in tools/test-requires and I am getting on a clean devstack install (with only keystone installed) :

stack@devstack:~/keystone$ /opt/stack/keystone/bin/keystone-manage db_sync [master]
Traceback (most recent call last):
  File "/opt/stack/keystone/bin/keystone-manage", line 28, in <module>
    cli.main(argv=sys.argv, config_files=config_files)
  File "/opt/stack/keystone/keystone/cli.py", line 164, in main
    return run(cmd, (args[:1] + args[2:]))
  File "/opt/stack/keystone/keystone/cli.py", line 147, in run
    return CMDS[cmd](argv=args).run()
  File "/opt/stack/keystone/keystone/cli.py", line 35, in run
    return self.main()
  File "/opt/stack/keystone/keystone/cli.py", line 54, in main
    driver = importutils.import_object(getattr(CONF, k).driver)
  File "/opt/stack/keystone/keystone/openstack/common/importutils.py", line 39, in import_object
    return import_class(import_str)(*args, **kwargs)
  File "/opt/stack/keystone/keystone/openstack/common/importutils.py", line 34, in import_class
    (class_str, str(exc)))
ImportError: Class Identity cannot be found (No module named iso8601)
Exception KeyError: KeyError(44501392,) in <module 'threading' from '/usr/lib/python2.7/threading.pyc'> ignored

this is because of keystone.token.core include :

from keystone.openstack.common import timeutils

which need iso8601