Loading VisualEditor with jQuery 3+Migrate (T124742; https://gerrit.wikimedia.org/r/322812) results in the following warning:
JQMIGRATE: jQXHR.error is deprecated and removed
- ..
- ve.init.mw.DesktopArticleTarget.loadFail
- ..
- ve.init.mw.ArticleTarget.load
- ve.init.mw.DesktopArticleTarget.activate
It seems loadFail() is given an jqXHR as first parameter. This matches the original documentation in parent class mw.ArticleTarget#loadFail, however I'm not sure if the code still expects this.
Perhaps it can be cleaned up as to not be passed anymore, or altered to not access its .error property, which is in fact, not an error representation, but a deprecated jqXHR method that is an alias of jQuery.Deferred#fail(), which adds a callback to the promise rejection handler.