/usr/share/doc/libdri2-dbg/changelog.Debian.gz is in libdri2-dbg 1.0.0~git20120510+26fee2e-0ubuntu2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/libdri2-dbg/../libdri2-1/changelog.Debian.gz