/usr/lib/x86_64-linux-gnu/libevent_extra-2.0.so.5 is in libevent-extra-2.0-5 2.0.21-stable-2ubuntu0.16.04.1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libevent_extra-2.0.so.5.1.9