[3dprinter-general] How to resolve gettext error "can't guess language"?

[Gregor Riepl]

>> gettext: resources/i18n/cs_CZ/cura.po: can't guess language
>> ...other po files follow...
>>
>> Full report: https://i18n.debian.org/l10n-pkg-status/c/cura.html
> 
> is the locale package installed? Is cs in the output of locale -a? The po file itself is fine. For me it works flawlessly.

If I execute the command locally, it doesn't report any errors.
As a matter of fact, all of the PO files verify ok, even though I have
only enabled some of the locales.

But I'd like to know why https://i18n.debian.org/ flags these errors.
Is there something wrong with this system? Do I have to contact
debian-l10n-devel at lists.alioth.debian.org for help?