+++ This bug was initially created as a clone of Bug #1968570 +++

+++ Description of problem:

The error message returned to the operator when trying to create installation with OpenShift version lower than 4.8 is slightly misleading

+++ Steps to Reproduce:

1. Create ClusterImageSet "openshift-v4.7.14" pointing to "quay.io/openshift-release-dev/ocp-release:4.7.14-x86_64"
2. Create AgentClusterInstall with imageSetRef "openshift-v4.7.14"
3. Create ClusterDeployment
4. Create InfraEnv

+++ Actual results:

ACI shows error "BackendError" with reason "The Spec could not be synced due to backend error: OCP version is not specified in OPENSHIFT_VERSIONS: 4.7"

IE shows error "ImageCreationError" with reason "Failed to create image: record not found"

+++ Expected results:

As an operator it's not completely clear to me that "OCP version is not specified [...]" is equivalent to the check being performed here (i.e. whether it's at least version 4.8

--- Additional comment from mhrivnak on 20210607T15:17:32

A k8s API message should not mention specific environment variables. Here, a more clear message would be something like "RHCOS image is not configured for version 4.7". A hint about where to go to configure it would be a bonus.