Use of "wgNamespaceNumber" is deprecated. Use mw.config instead.
This isn't really helpful. I'd prefer if the error recommended something like:
Use of "wgNamespaceNumber" is deprecated. Use "mw.config.get( 'wgNamespaceNumber' )" instead.
Or with a message like this:
Use of "addOnloadHook" is deprecated. Use jQuery instead.
Can this include a link? Or perhaps explain what "use jQuery" means?