- drop iso-639 and iso3166 dependencies in favor of pycountry
- remove the `STREAMLINK_USE_PYCOUNTRY` env var switch from setup.py
- move dependencies list from setup.py to setup.cfg
- update utils.l10n and its tests
- update Windows installer config
- update docs
instead of using DEFAULT_LANGUAGE.
This will prevent the LookupError from being raised unnecessarily
by the Localization._parse_locale_code call afterwards.
It will show this message when Localization is called by muxed hls or
dash streams.
```
$ streamlink ... --locale ru_RU
...
[plugin.dash][debug] Parsing MPD URL: ...
[utils.l10n][debug] Language code: ru_RU
```
or your local system code
```
$ streamlink ...
...
[plugin.dash][debug] Parsing MPD URL: ...
[utils.l10n][debug] Language code: xx_XX
```
* E265 - Fix spacing after comment hash for block comments.
* W293 - Remove trailing whitespace on blank line.
* E305 - Add missing 2 blank lines after end of function or class.
* E123 - Align closing bracket to match opening bracket.
* E202 - Remove extraneous whitespace before bracket.
* Remaining fixes.
The `pycountry` vs. `iso639+iso3166` l10n tests were broken so that the
only the `pycountry` tests were being run. This has now been fixed, which
uncovered a bug in the `iso3166` country lookup.