Attempt to add role to nonexistant user on tenant is not throwing an error

Attempt to add role to non existant user on tenant is not throwing an appropriate error message.

Expected Result:
Error message stating that user is not found should be thrown. i.e an error code of 404 should be thrown leading to Not Found exception.

Actual result:
Response code of 200 is returned and details of role in response body.

The response header and body are as follows:
{'date': 'Wed, 30 May 2012 15:20:07 GMT', 'content-type': 'application/json', 'content-length': '80', 'status': '200', 'vary': 'X-Auth-Token'}
{"role": {"id": "d1e7703c561148eca4826f0af79a3cc8", "name": "role-20991507068"}}

LOG:
----------
rajalakshmi_ganesan@pshys0183~json:-( >keystone --debug user-role-add --tenant_id 22de173542754eef8996521b731ae7ef --user 999 --role 66866c41031646439ed52da8a4f5d1a2
connect: (10.233.52.27, 5000)
send: 'POST /v2.0/tokens HTTP/1.1\r\nHost: 10.233.52.27:5000\r\nAccept-Encoding: identity\r\nContent-Length: 127\r\ncontent-type: application/json\r\nuser-agent: python-keystoneclient\r\n\r\n{"auth": {"passwordCredentials": {"username": "admin", "password": "muralik"}, "tenantId": "22de173542754eef8996521b731ae7ef"}}'
reply: 'HTTP/1.1 200 OK\r\n'
header: Content-Type: application/json
header: Vary: X-Auth-Token
header: Content-Length: 2229
header: Date: Wed, 30 May 2012 16:09:12 GMT
connect: (10.233.52.27, 35357)
send: u'PUT /v2.0/tenants/22de173542754eef8996521b731ae7ef/users/999/roles/OS-KSADM/66866c41031646439ed52da8a4f5d1a2 HTTP/1.1\r\nHost: 10.233.52.27:35357\r\nAccept-Encoding: identity\r\nContent-Length: 4\r\nx-auth-token: 63c1b98c11b9439b9554a8298ea1bdc8\r\ncontent-type: application/json\r\nuser-agent: python-keystoneclient\r\n\r\nnull'
reply: 'HTTP/1.1 200 OK\r\n'
header: Content-Type: application/json
header: Vary: X-Auth-Token
header: Content-Length: 69
header: Date: Wed, 30 May 2012 16:09:12 GMT
rajalakshmi_ganesan@pshys0183~json:-)>keystone --debug user-role-add --tenant_id 22de173542754eef8996521b731ae7ef --user alpha --role 66866c41031646439ed52da8a4f5d1a2
connect: (10.233.52.27, 5000)
send: 'POST /v2.0/tokens HTTP/1.1\r\nHost: 10.233.52.27:5000\r\nAccept-Encoding: identity\r\nContent-Length: 127\r\ncontent-type: application/json\r\nuser-agent: python-keystoneclient\r\n\r\n{"auth": {"passwordCredentials": {"username": "admin", "password": "muralik"}, "tenantId": "22de173542754eef8996521b731ae7ef"}}'
reply: 'HTTP/1.1 200 OK\r\n'
header: Content-Type: application/json
header: Vary: X-Auth-Token
header: Content-Length: 2229
header: Date: Wed, 30 May 2012 16:09:33 GMT
connect: (10.233.52.27, 35357)
send: u'PUT /v2.0/tenants/22de173542754eef8996521b731ae7ef/users/alpha/roles/OS-KSADM/66866c41031646439ed52da8a4f5d1a2 HTTP/1.1\r\nHost: 10.233.52.27:35357\r\nAccept-Encoding: identity\r\nContent-Length: 4\r\nx-auth-token: e3710202b5494d11a373b4e657bdfd05\r\ncontent-type: application/json\r\nuser-agent: python-keystoneclient\r\n\r\nnull'
reply: 'HTTP/1.1 200 OK\r\n'
header: Content-Type: application/json
header: Vary: X-Auth-Token
header: Content-Length: 69
header: Date: Wed, 30 May 2012 16:09:33 GMT
rajalakshmi_ganesan@pshys0183~json:-)>