Hi,
Lockdown.php is missing, is this on purpose? Version 1.30 had this file (https://gerrit.wikimedia.org/r/plugins/gitiles/mediawiki/extensions/Lockdown/+/REL1_30), but 1.31 lacks it (https://gerrit.wikimedia.org/r/plugins/gitiles/mediawiki/extensions/Lockdown/+/REL1_31)
The README in 1.31 still mentions "require_once( "$IP/extensions/Lockdown/Lockdown.php" );" as the way to install this extension, so I assume the file should still exist.
Thanks, have a nice day,
Cyber1000