/usr/share/doc/libubuntu-download-manager-client-dev/changelog.Debian.gz is in libubuntu-download-manager-client-dev 0.3+14.04.20140321-0ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/libubuntu-download-manager-client-dev/../libubuntu-download-manager-common0/changelog.Debian.gz