If no available preview generator supports to generate a preview for a resource/
language it's very unlikely that the next time the preview is requested it can
be created and served successfully. Therefore send a 404 Not Found instead of
503 Service Unavailable.
If no available preview generator supports to generate a preview for a resource/ language it's very unlikely that the next time the preview is requested it can be created and served successfully. Therefore send a 404 Not Found instead of 503 Service Unavailable.