In the CI for Z, we need the ability to perform a dynamic lookup of the RHCOS image to be used. Without this capability, we are going to be forced to hardcode an image or put together logic that essentially emulates what the installer would have done anyway. Since support for Z is being introduced in 4.2.z, this functionality will need to be added back in the release-4.2 branch.
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-2020:0395