We use UserWarning to report things like:
/srv/edge.launchpad.net/edge/launchpad-rev-11522/lib/lp/registry/model/projectgroup.py:429: UserWarning: shortlist() should not be used here. It's meant to listify sequences with no more than 15 items. There were 30 items.
However the stdout/stderr of the appservers is not automatically examined and analyzed, and request context is lost doing this.
Rather than a warning, this should be attached to an OOPS, and any request that hits this should generate a soft-oops no matter what.