The compat mode bits were an old workaround from when runroot was not part of koji. At this point, no one should be running a koji old enough for the workaround to be triggered. The runroot plugin should match the base version anyway.
Metadata Update from @mikem: - Issue set to the milestone: 1.14 - Issue tagged with: easyfix
PR #503
Commit be6e8215 fixes this issue
Commit a1551a78 fixes this issue
This issue has been migrated to Fedora Forge: https://forge.fedoraproject.org/koji/koji/issues/501
Please continue any further discussion there.