Add some error checking to ensure consistent MPI
Add some error checking to ensure consistent MPI

 - Make it harder for #359 or similar to happen again
 - #275 would have also helped catch this

sourceryinstitute/opencoarrays,zbeekman/opencoarrays,zbeekman/opencoarrays,sourceryinstitute/opencoarrays,sourceryinstitute/opencoarrays,zbeekman/opencoarrays