I like the use of `lang_code` here to disambiguate  which button corresponds to which language.

`class` should be hard-coded (see the previous line for an example).  And you need to find a way to localize the `Delete xx` string.  My suggestion:

```
            lang_description += sprintf("<div class='delete-language-button'> <button value='%s' type='button'>%s</button></div>", lang_code, sprintf(gettext('Delete %(lang_code)s', {lang_code: lang_code})));
```