/usr/lib/x86_64-linux-gnu/libpmount.so is in libpmount-dev 0.0.17-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libpmount.so.0.0.17
/usr/lib/x86_64-linux-gnu/libpmount.so.0.0.17