1: have an env with external Vms (at least one)
2: edit the cluster
Internal engine error is reported
Some descriptive validation error is reported that can not edit the cluster if there are external VMs in it.
Or it could ignore the external VMs and not try to update tham
Fails because the UpdateVmCommand.validate() returns false making the UpdateClusterCommand call setSucceeded(false) in because !updateVms()