As @frostyx and me discussed this today on IRC, i am creating a ticket. The issue is that there is no stacktrace when getting an error, after submitting a module build in COPR. Example:

I wanted to build a module in COPR. I did this:

copr-cli --debug build-module --yaml pegacornicus.yaml pegacornicus

I have got an error which was:

#  Debug log enabled  #
[09:55:18] {/usr/lib/python3.7/site-packages/urllib3/connectionpool.py:959} DEBUG - Starting new HTTPS connection (1): copr.fedorainfracloud.org:443
[09:55:18] {/usr/lib/python3.7/site-packages/urllib3/connectionpool.py:437} DEBUG - https://copr.fedorainfracloud.org:443 "POST /api_3/module/build/mcurlej/pegacornicus?ownername=mcurlej&projectname=pegacornicus HTTP/1.1" 500 80

This is not really helpful as i had no idea what is the problem. After some tinkering i found out that the format of my modulemd file was wrong. It would be nice if the error and its stacktrace would be printed out to the end user to see.