/usr/share/doc/libnet-sftp-ruby1.8/changelog.Debian.gz is in libnet-sftp-ruby1.8 1:2.0.5-2build1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/libnet-sftp-ruby1.8/../ruby-net-sftp/changelog.Debian.gz