Updates:
Status: WontFix
Comment #1 on issue 964 by pekka.klarck: WARN test result
http://code.google.com/p/robotframework/issues/detail?id=964
We have made a decision to use only two statuses: PASS and FAIL. In
addition to that you can use tags to add free classifiers to your tests and
then make tests critical or non-critical based on them. This has in
practice been enough in all projects we have been involved with.
There has been now and then requests to add new statuses such as SKIP,
WARN, IGNORE, ERROR, CRITICAL, etc. Clearly adding all of them makes no
sense. Generally agreeing what new statuses would be useful isn't possible
either because that depend on the context.
For a bit longer discussion related to this subject see issue 837 that also
was WontFixed. This has also been discussed few times on
robotframework-users mailing list.