/usr/lib/x86_64-linux-gnu/libdevmapper-event.so is in libdevmapper-dev 2:1.02.90-2.2+deb8u1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /lib/x86_64-linux-gnu/libdevmapper-event.so.1.02.1
/lib/x86_64-linux-gnu/libdevmapper-event.so.1.02.1