print project errors after all. sometimes.

print project errors after all. sometimes.

we evaluate prf files precisely, so we need to see their errors, as they
may give a hint why they terminated prematurely.
however, we prefix the errors with "WARNING:" to make them less scary.

Change-Id: Ia14953a5a9dc31af56ad6c338017dd5b85bb4494
Reviewed-by: hjk <hjk121@nokiamail.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>