After installing WikibaseLexeme extension in my fresh MediaWiki instance, I faced an issue trying to add Senses where the Language field for a gloss would not lookup and populate with proper language value.

Even if I get a textual representation of a language value, such as Afrikaans (af) or en-gb and put it manually in, it still appears not to process it properly and I get the following error:

I'm not sure if that's a bug in WikibaseLexeme function (or a feature), But I think adding the two extensions as (recommended?) prerequisites as part of WikibaseLexeme install instructions is a good idea.

Reproduce

1. Do not install/load CLDR and ULS extensions on your MediaWiki instance
2. Create a Lexeme
3. Try to add a Sense, filling in 1-or-more glosses with language codes
4. Save the sense form
5. You should an error message similar to the one in screenshot above