Good afternoon! On the Katello installation page, it is not noted that you will need the CentOS-7 GPG key, found at https://www.centos.org/keys/RPM-GPG-KEY-CentOS-7. On a fresh install of RHEL7, if this key is not imported, the centos-release-scl packages from the foreman repo can not be verified. Further, since they are from the foreman repo, yum will spit out an error saying that the foreman repo key is incorrect for those packages (which is accurate). This can be confusing for those less experienced with deploying Foreman/Katello.

I believe a step,
rpm --import https://www.centos.org/keys/RPM-GPG-KEY-CentOS-7
should be added to the required repositories step.