Running "python -m pip check" in every Python package

Now that we have automerge support and that the newer `pip` versions support `pip check` to check for a consistent environment, should we add this as a test to all Python packages?

I have added it to some packages and I see it failing quite often as downstream miss dependency updates when they do version updates.

Todos:

- [x] write a migrator (https://github.com/regro/cf-scripts/pull/787)
- [ ] write a check for the linter
- [ ] add test to skeleton
- [ ] add test to the default example recipe