Vlad Grevtsev

Reproduces also with ``` harness = Harness(charm.Charm) harness.begin() harness.charm._stored.set_default(is_started=False) harness.charm.on.config_changed.emit() ``` in the test code.

@jameinel here's a reproducer: https://github.com/exceptorr/charm-k8s-prometheus/tree/prepare-for-config-dynamic-reload - just uncomment the test back https://github.com/exceptorr/charm-k8s-prometheus/commit/ef04be0b44154d09ed3989cd96a77f9334913230#diff-62dd0694ddd90672dc34aa34f68aa827R61 and that's it!

> I was thinking it might be: https://github.com/exceptorr/charm-k8s-prometheus/blob/master/src/charm.py#L35 > But that class doesn't have a _stored attribute Yeah because you were looking at the `master` branch, while this code is...

I'd personally vote for https://palletsprojects.com/p/jinja/ - it's lightweight, well-known in the community and, actually, is already used in some charms (example: https://github.com/canonical/charm-nats/blob/master/.gitmodules#L4 and https://github.com/charmed-lma/charm-k8s-prometheus/pull/25/files#diff-8903239df476d7401cf9e76af0252622R4)