OpenShift Agent-based Installer not able to create image

Issue

The new Openshift Agent-based Installer fails with:

cannot generate ISO image due to configuration errors

Installation errors when no MAC address provided in agent-config.yml:

$ openshift-install --dir /home/xxx/sno-test agent create image
WARNING Capabilities: %!!(MISSING)s(*types.Capabilities=<nil>) is ignored
ERROR failed to write asset (Agent Installer ISO) to disk: cannot generate ISO image due to configuration errors
FATAL failed to fetch Agent Installer ISO: failed to load asset "Agent Config": invalid Agent Config configuration: Hosts[0].Interfaces[0].macAddress: Required value: 

There is no way of knowing in advance what the mac address of a new VM will be.