Thanks to [1], we can add comps file to modular compose which is useful for now, as current Anaconda needs at least some comps file available in repo.

However I have noticed that if we add comps to modular composes and getting of modular data fails, the compose continues with comps instead of raising error:

2017-10-19 14:39:05 [WARNING ] pdc_client module is not installed, support for modules is disabled

IMHO, a compose that has:

gather_source = 'module'

and module metadata cannot be obtained should fail.

[1] https://pagure.io/pungi/pull-request/764