What is the supportability of 'virsh snapshot-delete' and 'virsh snapshot-revert' command in Red Hat Enterprise Linux 7?

Issue

• virsh snapshot-delete command fails with the following messages.:

 # virsh snapshot-delete <vm_name> <snapshot_name>
   error: Failed to delete snapshot <snapshot_name> 
   error: unsupported configuration: deletion of 1 external disk snapshots not supported yet

• virsh snapshot-revert command fails with similar error messages stating this is unsupported:

 # virsh snapshot-revert <vm_name> <snapshot_name> --force --running
   error: unsupported configuration: revert to external disk snapshot not supported yet