* Start moving parts of yaml utils to own module
Move parts of yaml loader out of the single large file and start
to create the structure of the yaml loaders in Ansible [0].
[0]: https://github.com/ansible/ansible/tree/devel/lib/ansible/parsing/yaml
* Finish yaml migration, update tests and mocks
* Move code around to finish the migration
* Update the mocks so that `open` is patched in
`homeassistant.util.yaml.loader` instead of
`homeassistant.util.yaml`.
* Updated mypy ignores
* Updated external API of `homeasistant.util.yaml`, see below:
Checked what part of the api of `homeassistant.util.yaml` was actually
called from outside the tests and added an `__ALL__` that contains only
these elements.
Updated the tests so that references to internal parts of the API (e.g.
the yaml module imported into `homeassistant.util.yaml.loader`) are
referenced directly from `homeassistant.util.yaml.loader`.
In `tests/test_yaml.py` the import `yaml` refers to
`homeassistant.util.yaml` and `yaml_loader` refers to `~.loader`.
Future work that remains for the next iteration is to create a custom
SafeConstructor and refers to that instead of monkey patching `yaml` with
custom loaders.
* Update mocks in yaml dumper, check_config
## Description:
Fix a lint issue in credstash script.
**Related issue (if applicable):** fixes #<home-assistant issue number goes here>
**Pull request in [home-assistant.io](https://github.com/home-assistant/home-assistant.io) with documentation (if applicable):** home-assistant/home-assistant.io#<home-assistant.io PR number goes here>
## Example entry for `configuration.yaml` (if applicable):
```yaml
```
## Checklist:
- [ ] The code change is tested and works locally.
- [ ] Local tests pass with `tox`. **Your PR cannot be merged unless tests pass**
- [ ] There is no commented out code in this PR.
If user exposed functionality or configuration variables are added/changed:
- [ ] Documentation added/updated in [home-assistant.io](https://github.com/home-assistant/home-assistant.io)
If the code communicates with devices, web services, or third-party tools:
- [ ] New dependencies have been added to the `REQUIREMENTS` variable ([example][ex-requir]).
- [ ] New dependencies are only imported inside functions that use them ([example][ex-import]).
- [ ] New or updated dependencies have been added to `requirements_all.txt` by running `script/gen_requirements_all.py`.
- [ ] New files were added to `.coveragerc`.
If the code does not interact with devices:
- [ ] Tests have been added to verify that the new code works.
[ex-requir]: https://github.com/home-assistant/home-assistant/blob/dev/homeassistant/components/keyboard/__init__.py#L14
[ex-import]: https://github.com/home-assistant/home-assistant/blob/dev/homeassistant/components/keyboard/__init__.py#L23
* Don't treat typing as an "in-between" module for import order
That was a < 3.5 era thing.
* Tighten scope of some pylint unused-import disables
To avoid isort moving a top level one around, undesirably broadening its
scope.
* Fix packages deletion in check_config script
* The config key for packages is not present if core config validation
failed. We need to do a safe dict deletion using dict.pop.
* Add check_config test for bad core config
