About [[MediaWiki:Cx-sourceselector-dialog-error-page-and-title-exist/nb]]
Fragment of a discussion from Translating talk:MediaWiki
As you can see in MediaWiki:Cx-sourceselector-dialog-error-page-and-title-exist/qqq, all details are available:
MediaWiki:Cx-sourceselector-dialog-error-page-and-title-exist/qqq