ansible-hardening/doc/source/developer-notes/V-38683.rst

The Ansible task will use the pwck command to search for non-unique usernames on the system. If any matching usernames are found, an error will be printed and the playbook will fail.

NOTE: The pwck command will find other abnormalities on the system, including users that exist in /etc/passwd but not in /etc/shadow, and vice versa. If the playbook fails on this task, try to run this command on the system as root to find out what caused the failure:

pwck -rq