The package openstack-tempest-liberty-20160413.2.el7ost contains --remove feature and it's accessible from Liberty repositories since 2017-09-26 -> VERIFIED
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://access.redhat.com/errata/RHBA-2017:3067