Unexpected language code

[asa]

I ran a Google Pagespeed test on my instance and received the following message:

I can’t explain what’s causing it. Is there an error in the translator?

[Lilly (Lillian)]

(post deleted by author)

[Moin]

I think the invalid code comes from Discourse.

app/views/common/_hreflang_tags.html.erb

Maybe instead of hreflang="<%= locale %>" it should be hreflang="<%= locale.tr('_', '-') %>" to replace the underscore.