Since our tests include checking that coolr can access the rapl
interface, we should ensure that only runners having rapl will test the
code.

No need to trigger CI for things that are not ready.

flake8 is an automatic style checker. This is very useful to ensure that
we have a consistent style as more people start contributing to the
code.

We ignore coolr for now, as it's a big offender.

Gitlab CI support, for a py.test run inside the pipenv configuration.