Improve error message for fixed-outputs with references. (cherry picked from commit ff6de4a9ee6c3862db9ee5f09ff9c3f43ae7a088) Change-Id: I733c49760b9a3f1b76a6bece3b250b8579cd6cac
I733c49760b9a3f1b76a6bece3b250b8579cd6cac