The /usr/ports/print/hplip/files/pkg-message.in needs an update to reflect recent cups-base merge.
I think it can be removed. ugen(4) devices always exist even with ulpt(4) loaded and I don't see what extra functionality would be enabled by adding users to the cups group.
A commit references this bug: Author: tijl Date: Mon Mar 21 11:35:29 UTC 2016 New revision: 411554 URL: https://svnweb.freebsd.org/changeset/ports/411554 Log: Remove pkg-message. It's no longer needed and causing confusion. PR: 207920 Changes: head/print/hplip/Makefile head/print/hplip/files/pkg-message.in