pungi.global.log
[ERROR ] [FAIL] Image build (variant AtomicHost, arch ppc64le, subvariant AtomicHost) failed, but going on anyway. [IMAGE_BUILD ] [INFO ] Hardlinking /mnt/koji/packages/Fedora-AtomicHost/29_Update/20181226.0/images/Fedora-AtomicHost-29_Update-20181226.0.aarch64.qcow2 to /mnt/koji/compose/updates/Fedora-29-updates-testing-20181226.0/compose/AtomicHost/aarch64/images/Fedora-AtomicHost-29_Update-20181226.0.aarch64.qcow2
corresponding ppc64le taskid - https://koji.fedoraproject.org/koji/taskinfo?taskID=31664488
By looking at oz log and screenshot.ppm , nothing looks unusual to me.
I did a local (on latest F28 host) run of imagefactory on ppc64le with config from given koji taskid, image install finished successfully. I think this issue can be ppc64le builder specific.