if one attempts to install mediawiki on a system where database drivers are not installed, then fixes all the server side issues, mediawiki will continue to complain that database driver does not exist, as that is that it stores in a session cookie.

that is a wrong behavior, and server configuration/state should never live in user sessions.

deleting a cookie makes it work fine

reproduction:
on a machine without e.g. php5-mysql try installing mediawiki, then install php5-mysql and retry installer - it will fail.

Version: unspecified
Severity: normal