Code review comment for ~hloeung/charm-telegraf:master

Yes, please open an internal discussion with your team.

@txiao, it isn't Juju that uses the `runs-on` but rather `charmcraft`, the tooling used to build said charm. The way it is set up in `charm-telegraf` though, with `build-on` in addition to the pinned versions in `wheelhouse.txt` doesn't really make this limited to the series defined in `runs-on`. Not to mention that with `charm/2.x/stable`, it uses the bundled python 3.6 with the `charm` snap.

As for limiting python packages, sadly, it's needed as newer releases of python packages will (eventually) drop support for certain python versions. layer-basic, used by reactive charms, has bunch of limitations for this reason, see:

| https://github.com/juju-solutions/layer-basic/blob/master/wheelhouse.txt