https://phabricator.wikimedia.org/maniphest/ shows:
>>> UNRECOVERABLE FATAL ERROR <<< Declaration of WMFSubscribersPolicyRule::applyRule() must be compatible with PhabricatorPolicyRule::applyRule(PhabricatorUser $viewer, $value, PhabricatorPolicyInterface $object) /srv/phab/libext/security/src/policy/WMFSubscribersPolicyRule.php:0 ┻━┻ ︵ ¯\_(ツ)_/¯ ︵ ┻━┻