* Enable BMW component to be unit system aware
* lint fixes
* use constants for config entries
* remove configuration from component and rely only on HA config of unit_system
* remove unused import
* update code to reflect feedback
* lint fixes
* remove unnecessary comments
* rework return statement to satisfy pylint
* more lint fixes
* add tests for volume utils
* lint fixes
* more lint fixes
* remove unnecessary comments
## Description:
More fixes flagged by pylint 2 that don't hurt to have before the actual pylint 2 upgrade (which I'll submit soon).
## Checklist:
- [ ] The code change is tested and works locally.
- [x] Local tests pass with `tox`. **Your PR cannot be merged unless tests pass**
## Description:
Make typing checks more strict: add `--strict-optional` flag that forbids implicit None return type. This flag will become default in the next version of mypy (0.600)
Add `homeassistant/util/` to checked dirs.
## Checklist:
- [x] The code change is tested and works locally.
- [x] Local tests pass with `tox`. **Your PR cannot be merged unless tests pass**
Marc Mueller
Ville Skyttä
Philip Allgaier
Franck Nijhof
Bas Nijholt
Franck Nijhof
Paulus Schoutsen
MatthewFlamm
uchagani
Jason Hu
Andrey
Fabian Affolter
Paulus Schoutsen