So Foreman recently changed their rubocop settings to require a trailing comma in arrays and hashes. (New trailing comma style in foreman.git)
I personally feel that this is a far better convention than requiring that their not be a trailing comma (as was the case before).
Mainly because it improves the readability of diffs.
However, it appears Katello is still using the “old” rubocop settings, and the only thing worse than the wrong convention is inconsistent conventions.
My vote is for Katello to go through the same adjustment in rubocop settings that Foreman went through.