They raise the following error: TypeError: write() argument must be str, not bytes. A fix is in PR #735.
TypeError: write() argument must be str, not bytes
Metadata Update from @tkopecek: - Issue set to the milestone: 1.16
Commit 22a7998f fixes this issue
This issue has been migrated to Fedora Forge: https://forge.fedoraproject.org/koji/koji/issues/738
Please continue any further discussion there.