/usr/share/doc/libustr-dev/README is in libustr-dev 1.0.4-3ubuntu2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/libustr-dev/../libustr-1.0-1/README
/usr/share/doc/libustr-dev/../libustr-1.0-1/README