Bug#248951: "en" is not a valid locale, but is added to locale.gen

[Christian Perrier <bubulle@debian.org>]

Quoting Joey Hess (joeyh@debian.org):
> Package: base-config
> Version: 2.21
> Severity: normal
> Tags: d-i
> 
> If I tell d-i my language is English, but pick Brazil as my country,
> I get "en" in /etc/locale.gen. This makes perl spit out ugly errors, and
> is not a valid locale, so it should not be added.

Yeah, we have to deal with these issues triggered by the use of the
"all world country" screen in countrychooser (Nikolai raised the same
for ru in DE)

IMHO, you're right assigning this to base-config. It should check
debian-installer/locale against /usr/share/i18n/SUPPORTED before
adding this value to /etc/locale.gen. If the locale is invalid, it
needs to fallback to another one, which could be picked up in another
variable.