Docutils has no localization for 'eu

[zunbeltz]

I am setting a subsite using i18n_subsites plugin for languages english, spanish and basque. The configuration looks like this:

I18N_SUBSITES = {
    'en': {
    'SITENAME': 'From chaos to data',
    'SITEURL': 'htpp://zunbeltz.gitlab.io/site/en',
    },
    'es': {
    'SITENAME': 'From chaos to data',
    },
    'eu': {
    'SITENAME': 'From chaos to data',
    'SITEURL': 'htpp://zunbeltz.gitlab.io/site/eu',
    },

Even if I only have pages with en and es lang tags, I get the following error at build time:

"pelican" "/builds/zunbeltz/site/content" -o "/builds/zunbeltz/site/public" -s "/builds/zunbeltz/site/publishconf.py" 
[06:42:11] WARNING  Docutils has no localization for 'eu'. Using 'en'  log.py:89
                    instead.                                                    
[06:42:12] CRITICAL KeyError:                                    __init__.py:666
                    '/builds/zunbeltz/site/content/pages/About.m                
                   d'                  

I am building in a docker image base on python:3.12-alpine; locale -a shows that the eu_ES locale is present. I installed the lang py3-docutils musl musl-utils musl-locales tzdata packages. What can be missing?

[zunbeltz]

Sorry for polluting the tracker. Everything fixed by removing the translate tag and installing python-babel.