Steps to reproduce

1. deploy a fresh installation of MediaWiki
2. make wiki private by setting in LocalSettings.php:

$wgGroupPermissions['*']['edit'] = false;
$wgGroupPermissions['*']['read'] = false;

1. navigate to the wiki, notice that any page will say "Connection required"
2. hover mouse cursor over "Log in" link on the top right corner to display its "title" attribute

Actual result
The title reads "You are encouraged to log in; however, it is not mandatory [alt-shift-o]".

Expected result
Since the wiki is private, unregistered users cannot view or edit pages, hence the title attribute of the "log in" link should read something like "You need to log in to use this wiki [alt-shift-o]".

Note
This issue has been noticed on a french language installation.