Last modified: 2014-04-04 14:33:22 UTC
When I enter wrong username in https://test2.wikipedia.org/w/index.php?title=Special:UserLogin&action=submitlogin&type=login&returnto=Main+Page , I get a "Wikipedia's signup page" link which links to https://en.wikipedia.org/w/index.php?title=Special:UserLogin&type=signup rather than https://test2.wikipedia.org/w/index.php?title=Special:UserLogin&type=signup&returnto=Main+Page
That's due to the local message https://test2.wikipedia.org/wiki/MediaWiki:Nosuchuser
As per comment 1 this needs to be fixed on-wiki, hence out of scope for Bugzilla.