As of Mageia 6, when you attempt an upgrade via the classical installer, it will ask you if you *want* to configure network media.
Not enabling them is not supported and will most of the time result in a broken upgrade, as there aren't enough packages on the installation media to do a full upgrade.
We should therefore stop asking users, and simply *request* that they configure network media. If such media can't be configured (network not working), then the upgrade should be prevented.
But we have to be careful about this, as this would require different behavior when the installer is running off the DVD vs. when it's bootstrapped via boot.iso/all.img, where an upgrade would have access to the full repository already (possibly via a local hard disk, not the network) and should be able to proceed just fine.