optional_arches should be a list.
But a single string like 'i386' should work in this case.

Can you try a new build with optional_arches=['i386'] here? it looks your build task is triggered by API call.

The task was started by koji spin-livemedia Fedora-KDE-Live Rawhide f28 i386,x86_64 fedora-live-kde.ks --can-fail=i386 … command.

ah, found the problem. kojicli doesn't really change the --can-fail value to list.

There is no problem with task submission, that works exactly as expected. The only problem we're running into is that the CLI exits with return code 1 even when the task finishes successfully but has some failed subtasks.

We can work around this in Pungi, but at least it would be nice to have some documentation or statement what does the exit code on the client side actually mean.

There is no problem with task submission, that works exactly as expected. The only problem we're running into is that the CLI exits with return code 1 even when the task finishes successfully but has some failed subtasks.

Oh, we should dig into TaskWatcher to normalize the return code with can-fail feature.
What I mentioned above is a small bug, which doesn't impact current functionality.

PR #703

Commit 5574ad78 fixes this issue

Commit 73ebc0c9 fixes this issue

This issue has been migrated to Fedora Forge:
https://forge.fedoraproject.org/koji/koji/issues/696

Please continue any further discussion there.