'List users in group.
For a full list of available parameters, please refer to the official
API reference:
http://developer.openstack.org/api-ref/identity/v3/#list-users-in-group'

def list_group_users(self, group_id, **params):

    url = ('groups/%s/users' % group_id)
    if params:
        url += ('?%s' % urllib.urlencode(params))
    (resp, body) = self.get(url)
    self.expected_success(200, resp.status)
    body = json.loads(body)
    return rest_client.ResponseBody(resp, body)
