( [nativecode=Access denied for user: 'wiki@localhost' (Using password: YES)] ** mysql://wiki:XXXXXXXX@localhost/wiki)

It's just that we missed something. Like in the tutorial, make sure the following line is uncommented, and make sure the username and password can access the database (the DB name in this case is 'phpwiki')

'dsn' => 'mysql://username:password@localhost/phpwiki'

I hope this helps someone, as I was scratching my head for much too long on this simple mistake ;)