The commenting out of the 'banaction' variable in commit 0a1f92c breaks at least some jails with default settings, like sshd. The line action_ = %(banaction)s... in jail.conf requires that variable:
ERROR Failed during configuration: Bad value substitution: option 'action' in section 'sshd' contains an interpolation key 'banaction' which is not a valid option name. Raw value: '%(action_)s'