When request with invalid/not-existing Trust ID is send, the 404 response "message" contains only that ID, not a whole 'sentence' as in other cases.

Discovered with openstack-keystone-2013.1.1-1.el6ost.


Issue request like:
> GET /v3/OS-TRUST/trusts/YOUR_INVALID_ID
or 
> GET /v3/OS-TRUST/trusts/YOUR_INVALID_ID/roles # etc

Reply looks like:
> {u'error': {u'code': 404,
>            u'message': u'YOUR_INVALID_ID',
>            u'title': u'Not Found'}}

For other requests it mostly looks like:
> {u'error': {u'code': 404,
>            u'message': u'Could not find role: b0f22e0104654f5699f801fe90761365',
>            u'title': u'Not Found'}}

So the "Could not find <subject-type>: " part of message is missing here.