* Replace `noqa` comments in `assert...` method definitions with
a configuration option to ignore these names.
* Use the `__all__` variable to specify importable items from the
module, replacing `*` imports and `noqa` comments for unused imports.
* Address issues with poorly named variables and methods by renaming
them appropriately.
- Fix imports
- Fix pytest issues
- Do not assign lambda as variable
- Use isinstance instead of type to check type
- Rename ambiguously named variables
- Name custom errors with Error suffix
And move the definition to a shared module.
The problem was that EmbedartCliTest ran `_common.TestCase.setUp`
method which initialised temporary directory for the tests AND ran
`helper.TestHelper.setup_beets` method which initialised another set of
temporary directories. This meant that the first set of directories
could not be tracked down for the cleanup.
- generic method to check if operation was performed
- add test of deinterlace operation
- add test for multiple operations performed if required (fails on master)
External Python packages interfacing beets may want to use an in-memory
beets library instance for testing beets-related code.
The `TestHelper` class is very helpful for this purpose.
Previously `TestHelper` was located in the `test/` directory.
Now it is part of `beets` itself (`beets.test.helper.TestHelper`) and
can be easily imported.
