In Gerrit change 321406[1] and related patches,[2] I've proposed code to allow the MediaWiki action API to return errors and warnings in languages other than English. Feedback and code review would be appreciated.

A detailed description of the proposed changes is posted at https://www.mediawiki.org/wiki/API/Architecture_work/i18n#Warnings_and_errors. Summary:

• For clients of the API, some error codes will change, particularly from query submodules. If you're trying to parse the human-readable error and warning text, these also are likely to change. A few modules that returned error or warning text in a non-standard manner have been changed. For the most part, though, client code should not need updating since the default is backwards-compatible.
• For extension authors, several ApiBase methods are deprecated and should be replaced. The existing patches[2] may serve as examples.
  

 [1]: https://gerrit.wikimedia.org/r/#/c/321406/
 [2]: https://gerrit.wikimedia.org/r/#/q/topic:api-error-i18n/T47843