There's a discussion thread starting here: https://lists.debian.org/debian-mentors/2017/01/msg00322.html
about mpirun (a front end provided by openmpi to run a user program) refusing, by default, to run as root for mpgrafic, a program that uses mpi. This would affect any other debian package using openmpi if that package has a test run under dh_auto_test, unless that package explicitly adds an option --allow-run-as-root. Either having lots of failed builds, or having lots of packages run with a default option --allow-run-as-root, both sound like bad choices to me. Cheers Boud