+++ This bug was initially created as a clone of Bug #2011951 +++

+++ This bug was initially created as a clone of Bug #2011896 +++

Because:

Upgradeable=False

  Reason: MultipleReasons
  Message: Cluster cannot be upgraded between minor versions for multiple reasons: AdminAckRequired,IncompatibleOperatorsInstalled

doesn't include all the useful information needed to resolve those issues.  We should pivot to using the same approach we use today when aggregating multiple Upgradeable=False ClusterOperators, and use a bulleted list to append all the constituent messages.

The CVO's current logic goes way back, but the need to urgently fix this begins in 4.8.14, when we grew admin-ack via bug 1999092, colliding with OLM's IncompatibleOperatorsInstalled, which a lot of 4.8 clusters were already experiencing.

--- Additional comment from W. Trevor King on 2021-10-07 17:24:30 UTC ---

Verification should look something like:

1. Install a version with the fix.
2. Put something in spec.overrides to trigger ClusterVersionOverridesSet:

     $ oc patch clusterversion version --type json -p '[{"op": "add", "path": "/spec/overrides", "value": [{"kind": "Deployment", "group": "apps/v1", "name": "network-operator", "namespace": "openshift-network-operator", "unmanaged": true}]}]'

3. Create a ClusterOperator to trigger ClusterOperatorsNotUpgradeable:

     $ cat co.yaml 
     apiVersion: config.openshift.io/v1
     kind: ClusterOperator
     metadata:
       name: testing
     spec: {}
     $ oc apply -f co.yaml
     $ oc proxy &  # working around the lack of --subresource: https://github.com/kubernetes/kubernetes/pull/99556
     [1] 16920
     Starting to serve on 127.0.0.1:8001
     $ curl -k -XPATCH -H "Accept: application/json" -H "Content-Type: application/json-patch+json" 'http://127.0.0.1:8001/apis/config.openshift.io/v1/clusteroperators/testing/status' -d '[{"op": "add", "path": "/status", "value": {"conditions": [{"lastTransitionTime": "2021-08-31T01:01:01Z", "type": "Upgradeable", "status": "False", "reason": "Testing", "message": "Testing upgradeable https://example.com/a."}]}}]'
     $ fg
     oc proxy
     ^C

3. Wait a minute or so for the CVO to notice.

4. Check the 'oc adm upgrade' output.  It should include:

     Upgradeable=False

     Reason: MultipleReasons
     Message: Cluster should not be upgraded between minor versions for multiple reasons: ClusterVersionOverridesSet,Testing
     * Disabling ownership via cluster version overrides prevents upgrades. Please remove overrides before continuing.
     * Cluster operator testing should not be upgraded between minor versions: Testing upgradeable https://example.com/a.

5. Check the web-console output at:

   * The cluster settings page: ${CONSOLE}/settings/cluster
   * The ClusterVersion detail page ${CONSOLE}/k8s/cluster/config.openshift.io~v1~ClusterVersion/version

   They should both include the full message, clearly formatted.