Should start with a warning, and move after one year to users having confirm that they allow pqckqges to execute setup.py and ultimatrly not allow it any more.
This would probably break too much of the ecosystem, since many top Python packages include native extensions that can only be built with a dynamic `setup.py`.
Wheels are solving that problem, but it's likely going to be many years before warning about `setup.py` is reasonable and not disruptive to the majority of legitimate users.
