MediaWiki:Config-pg-not-in-role

The account you specified for the web user already exists. The account you specified for installation is not a superuser and is not a member of the web user's role, so it is unable to create objects owned by the web user.

MediaWiki currently requires that the tables be owned by the web user. Please specify another web account name, or click "back" and specify a suitably privileged install user.