Comment 1 for bug 2015330

Yes, you are correct. The https://opendev.org/openstack/nova/src/branch/master/nova/api/openstack/compute/servers.py#L813 check suggest an intention that we check for the external attach already in the nova-api. But in reality we did not. I mark this as valid but as a wishlist. Feel free to propos an improvement that handle this.