overcloud.pem comes from https://opendev.org/openstack/tripleo-heat-templates/src/branch/master/environments/ssl/enable-tls.yaml#L37
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-2020:2114