create_service() returns 500 Internal Server Error when bad keyword arg (XML only)

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ERROR: GET Service
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Traceback (most recent call last):
  File "/home/jpipes/repos/tempest/tempest/tests/identity/admin/test_services.py", line 62, in test_create_get_delete_service
    resp, _ = self.client.delete_service(service_data['id'])
UnboundLocalError: local variable 'service_data' referenced before assignment
-------------------- >> begin captured logging << --------------------
tempest.common.rest_client: ERROR: Request URL: http://127.0.0.1:35357/v2.0/OS-KSADM/services
tempest.common.rest_client: ERROR: Request Body: <?xml version="1.0" encoding="UTF-8"?>
<service xmlns="http://docs.openstack.org/identity/api/ext/OS-KSADM/v1.0" type="type--9743" description="description-769556" name="service-722762"/>
tempest.common.rest_client: ERROR: Response Headers: {'date': 'Thu, 04 Oct 2012 16:42:05 GMT', 'vary': 'X-Auth-Token', 'content-length': '284', 'status': '500', 'content-type': 'application/xml'}
tempest.common.rest_client: ERROR: Response Body: {'message': "An unexpected error prevented the server from fulfilling your request. create_service() got an unexpected keyword argument 'service'", 'code': '500', 'title': 'Internal Server Error'}

Keystone should return a 400 Bad Request if there are invalid arguments/query params supplied to OS-KSADM/ requests, not a 500.