Return code for rebuild with non-existent image changed

The tempest test

ERROR: Negative test: The server rebuild for a non existing server should not

recently broke because nova started returning 400 and it recently was returning 400.
Was this intentional?

Either the code or the test needs to be changed.

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ERROR: Negative test: The server rebuild for a non existing server should not
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Traceback (most recent call last):
  File "/cygdrive/c/source/tempest/tempest/tests/test_server_actions.py", line 158, in test_rebuild_nonexistant_server
    adminPass='rebuild')
  File "/cygdrive/c/source/tempest/tempest/services/nova/json/servers_client.py", line 217, in rebuild
    self.headers)
  File "/cygdrive/c/source/tempest/tempest/common/rest_client.py", line 100, in post
    return self.request('POST', url, headers, body)
  File "/cygdrive/c/source/tempest/tempest/common/rest_client.py", line 136, in request
    raise exceptions.BadRequest(resp_body['badRequest']['message'])
BadRequest: Bad request
Details: Bad request
Details: Invalid imageRef provided.
-------------------- >> begin captured logging << --------------------
tempest.common.rest_client: ERROR: Request URL: http://172.18.0.146:8774/v2/30db781b8c044409810ab5bdcd175968/servers/999/action
tempest.common.rest_client: ERROR: Request Body: {"rebuild": {"personality": [{"path": "/etc/rebuild.txt", "contents": "VGVzdCBzZXJ2ZXIgcmVidWlsZC4="}], "metadata": {"rebuild": "server"}, "name": "server36933620389", "imageRef": "346f4039-a81e-44e0-9223-4a3d13c907", "adminPass": "rebuild"}}
tempest.common.rest_client: ERROR: Response Headers: {'date': 'Fri, 23 Mar 2012 16:14:11 GMT', 'status': '400', 'content-length': '70', 'content-type': 'application/json; charset=UTF-8', 'x-compute-request-id': 'req-a582eee4-ec5c-483b-b97d-e1dd7deb70b7'}
tempest.common.rest_client: ERROR: Response Body: {u'badRequest': {u'message': u'Invalid imageRef provided.', u'code': 400}}
--------------------- >> end captured logging << ---------------------