On 2013-10-04 the Extension matrix bot stopped its service on mw.org. Since MediaWiki's Installer references the extension matrix with message 'Config-extension-link' I figure that the bot should be fixed. Since the original author of the bot seems to not be active any longer I am reporting this issue here, hopefully at the right spot. The extension matrix is quite useful so removing the reference does not appear to be an option to me. Thank you for your support.
The source code of the bot seems to be at this spot