/usr/share/doc/libctpp2-2-dbg/changelog.Debian.gz is in libctpp2-2-dbg 2.8.3-9ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/libctpp2-2-dbg/../libctpp2-2/changelog.Debian.gz
/usr/share/doc/libctpp2-2-dbg/../libctpp2-2/changelog.Debian.gz