Apart from breaking my system somewhat, I tried again, and I think you shouldn't pass -E GUIX_LOCPATH, because this will refer to something outside the environment. Instead, you should let the manifest set that for you. It will read po/LINGUAS to figure out which locales to bring in the environment.

Le 21 mai 2021 12:04:00 GMT-04:00, Tissevert <tissevert+guix@marvid.fr> a écrit :
>Hi !
>
>I'm afraid I saw your message too late because I have exactly the same
>problems
>you describe in https://issues.guix.gnu.org/47623 which you've just
>closed.
>
>I too have no ~/.guix-profile/lib/locale but
>~/.guix-profile/lib/locales exists
>and allows the build to complete.  So I don't know but could this
>~/.guix-profile/lib/locale with no trailing 's' be a left-over from a
>previous
>version of some software that used to build it at that location or
>something ?
>My install of guix is pretty recent (~3 months).
>
>From what I understood from the original issue, I checked $GUIX_LOCPATH
>and saw
>it contained only my current system's, /run/current-system/locale,
>which, when
>shared in place of this hypothetical `locales?` in $HOME/.guix-profile
>also
>allows haunt to build the site correctly (it produces something,
>reports
>success, and browsing what it serves looks like the official website).
>
>Hope that helps : )
>
>Tissevert
>
>Le Fri, May 21, 2021 at 01:53:43PM +0000, Luis Felipe a écrit :
>> Hi,
>> 
>> I've never been able to build and run the internationalized website
>correctly following the instructions on the README. I even thought
>there was a typo in the instructions
>(https://issues.guix.gnu.org/47623), but it seems there is actually a
>particular problem on my side that I don't know how to resolve. So I
>could use a little help.
>> 
>> The problem seems to be that the instructions on the README expect a
>"$HOME/.guix-profile/lib/locale" directory to exist, but it doesn't
>exist here. There is a "$HOME/.guix-profile/lib/locales" directory
>instead (note the plural name).
>> 
>> I've tried building and running the website using the "locales"
>directory to work around the issue. It used to build most of the time,
>but with enconding issues. Running the website almost always failed
>with some error about invalid arguments to "setlocale"), so I used
>plane "haunt serve".
>> 
>> Currently, though, using guix 1f68568 and guix website f7ca68f,
>building fails for me everytime I run this:
>> 
>> ★★★★★★★★★★★★★★★★★★★★
>> $ GUIX_WEB_SITE_LOCAL=yes guix environment -C -m manifest.scm -E
>GUIX_LOCPATH -E LANG --share=$HOME/.guix-profile/lib/locales -E
>GUIX_WEB_SITE_LOCAL --share=/tmp -- haunt build
>> guile: warning: failed to install locale
>> Backtrace:
>>            2 (primitive-load
>"/gnu/store/yzaxlqmiraznba4yf2cyqpyla9q?")
>> In haunt/ui.scm:
>>     131:2  1 (haunt-main _ "build")
>> In unknown file:
>>            0 (setlocale 6 "")
>> 
>> ERROR: In procedure setlocale:
>> In procedure setlocale: Invalid argument
>> ★★★★★★★★★★★★★★★★★★★★
>> 
>> 
>> So I haven't been able to work much on the website for a long time. I
>don't know what's going on...
>> 
>> 
>> ---
>> Luis Felipe López Acevedo
>> https://luis-felipe.gitlab.io/
>>