Scheduling failure reason is empty when no executors are found (pools not configured)

[Sovietaced]

We recently upgraded Armada and we found that jobs were no longer being scheduled. The scheduling reasons were all empty string. After digging into the code I discovered that the root cause was no executors being iterated over in the default pool. This new behavior was introduced in https://github.com/armadaproject/armada/pull/3988 where pools are required to be explicitly configured on the scheduler. Anyway, there should be a more user friendly error message when scheduling fails for these reasons.

[dejanzele]

Hey,

Thanks for reporting this!

We acknowledge this could be improved, though it's not a pressing issue on our end at the moment. If you're interested in making a PR, we'd gladly review and support you through it.

Let us know if you'd like to proceed!