--== VM CONFIGURATION ==--

          The following appliance have been found on your system:

          [1] - The oVirt Engine Appliance image (OVA) - 4.2-20180903.1.el7

          [2] - Directly select an OVA file

          Please select an appliance (1, 2) [1]:

[ INFO  ] Verifying its sha1sum

[ INFO  ] Checking OVF archive content (could take a few minutes depending on archive size)

[ INFO  ] Checking OVF XML content (could take a few minutes depending on archive size)

          Please specify the size of the VM disk in GiB: [50]:

[ INFO  ] Connecting to Engine

[ INFO  ] The hosted-engine storage domain has enough free space to contain a new backup disk.

[ INFO  ] Checking version requirements

[ INFO  ] Checking metadata area

[ INFO  ] Hosted-engine configuration is at a compatible level

[ INFO  ] Connecting to Engine

[ ERROR ] Cluster Default is at version 4.2 which is not supported by this upgrade flow. Please fix it before upgrading.

[ ERROR ] Failed to execute stage 'Environment customization': Unsupported cluster level

[ INFO  ] Stage: Clean up

[ INFO  ] Generating answer file '/var/lib/ovirt-hosted-engine-setup/answers/answers-20180920145828.conf'

[ INFO  ] Stage: Pre-termination

[ INFO  ] Stage: Termination

[ ERROR ] Hosted Engine upgrade failed

          Log file is located at /var/log/ovirt-hosted-engine-setup/ovirt-hosted-engine-setup-20180920145733-doc2cu.log

Any ideas on this, attached full logs for detail.