Re: [gentoo-dev] LINGUAS to be removed from USE_EXPAND

On Thu, 28 Dec 2017, Ulrich Mueller wrote:
> Last year we had announced introduction of a new L10N variable
> intended to replace LINGUAS as a USE_EXPAND variable [1]. Since then,
> many packages have been converted to the new variable.
>
> The next step in the conversion will be removal of LINGUAS from
> USE_EXPAND, which means that LINGUAS will become a normal variable,
> maintaining the standard gettext behaviour. For a transition time,
> all linguas_* flags currently existing in packages' IUSE will be
> added to use.desc, but will be removed again when conversion of the
> remaining packages is complete.
The package sci-mathematics/maxima for ages uses linguas_* flags for 
installing translated documentation, the possible values of * are

de es pt pt_BR

This usage is, I suppose, wrong. I tried simply to replace all linguas_ to 
l10n_ in the ebuild, but repoman complains about pt_BR.

What is the correct mechanism to install translated documentation 
depending on the user's wishes?

Andrey