mbs-manager raises an exception if the module build fails. This should just print stderr and exit with a non-zero exit code. We've been getting bug reports about these at: https://bugzilla.redhat.com/show_bug.cgi?id=1730323
Please note that rpkg may need to be adjusted for this.
It would be good to fix this after migrating mbs-manager to a new CLI framework mentioned in FACTORY-4876.
Commit e5c51d92 fixes this issue
This issue has been migrated to Fedora Forge: https://forge.fedoraproject.org/koji/mbs/issues/1364
Please continue any further discussion there.