## Description
Replace logout message with toast
[HIG](https://developer.gnome.org/hig/patterns/feedback/toasts.html)
Fixes#758
## Type of change
<!-- What type of change does your pull request introduce? Put an `x` in
the appropriate box . -->
- [ ] Bugfix (Change which fixes an issue)
- [ ] New feature (Change which adds new functionality)
- [x] Enhancement (Change which slightly improves existing code)
- [ ] Breaking change (This change will introduce incompatibility with
existing functionality)
## Testing
- [x] I have tested my changes and verified that they work as expected
<!-- Make sure you did this step before marking your PR as ready for
merge. -->
## Description
This PR refactors a few operations to make the code handle edge cases
efficiently with marginal performance improvements.
## Type of change
- [ ] Bugfix (Change which fixes an issue)
- [ ] New feature (Change which adds new functionality)
- [x] Enhancement (Change which slightly improves existing code)
- [ ] Breaking change (This change will introduce incompatibility with
existing functionality)
## Changelog <!-- This is optional, but highly appreciated. -->
- Stores the comma separated string representation of valid versions for
later use in raising exceptions.
- Uses tuple for `async_data` in `ShellTheme` since its members are
immutable.
- Uses tuple decomposition to assign theme variant and preset from
`async_data` later.
- Replaces `Gio.File.make_directory_with_parents` with Python's builtin
`os.makedirs` with `exist_ok` as True to implicitly create directories
when nonexistent.
- Instead of relying on `KeyError`s when accessing dictionary values,
the `get` method is used to supply a default value.
- When a key might exist in one dictionary, the `get` method (which may
return `None`) is coupled with the nullish `or` operator to use the
value that is not `None`.
- Uses predefined `main_source` attribute as argument to the
`_compile_sass` function.
- Uses the walrus operator to scope a template match to the condition
when it is not `None`.
- Removes unnecessary implicit `.close()`s on file handles when using
context managers.
## Testing
- [x] I have tested my changes and verified that they work as expected
<!-- Make sure you did this step before marking your PR as ready for
merge. -->
### How to test the changes
<!-- Optional, it can speed up review process if you provide the
information on how to test your changes. -->
Just run `./local.sh`
