Issue
wgGlobalVarConfig::get: undefined option: 'InterwikiSortingAlwaysSort' exception
in Wikidata/extensions/Wikibase/client/includes/Hooks/InterwikiSortingHookHandlers.php
Example of user-facing consequence
The two following pages have been modified this morning, and since they display the following errors, with Firefox or Chrome (emptied cache):
https://fr.wikibooks.org/wiki/Faire_du_pl%C3%A2tre : [WIdFygpAMCYAAFJajZsAAABV] 2017-01-24 12:17:15: Erreur fatale de type « ConfigException »
https://fr.wikibooks.org/wiki/MediaWiki_pour_d%C3%A9butants/Installer_des_extensions : [WIdF2gpAMFAAAKyXJW0AAAGJ] 2017-01-24 12:17:30: Erreur fatale de type « ConfigException »
Their history is all right.