Code review comment for ~jcastets/cloud-init:scaleway-datasource

Everything should be fixed.

* I updated the header of cloudinit/sources/DatasourceScaleway. Is it what you expect?
* on_scaleway doesn't rely on network anymore. It checks if "scaleway" is in /var/run/scaleway, in the commandline, or in DMI data.
* Made some unittests
* requests.requests creates a requests.Session object and calls session.request: https://github.com/requests/requests/blob/master/requests/api.py#L57 ; so my change should be backward compatible

If you need any precision or change, feel free to ask.

Since the datasource no longer makes network requests, is there a chance to enable it by default?

Thanks,