Description of problem:
when create edge-installer on the blueprint with a hostname, the image creation will fail, but the return error message is just a popup saying 'image create failed', that's not enough for customer to understand what's going wrong, only if they are very familiar with ostree images.

For example, the same case in command line with get error message like "unsupported blueprint customizations found for boot ISO image type "edge-installer": (allowed: User, Group)"

This error message is also not very detailed, but it at least, let me know that something is wrong with customizations in blueprint.

Version-Release number of selected component (if applicable):

How reproducible:
100%

Steps to Reproduce:
1.
2.
3.

Actual results:

Expected results:

Additional info: