/usr/share/doc/libwww-mechanize-ruby/changelog.Debian.gz is in libwww-mechanize-ruby 1.0.0-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/libwww-mechanize-ruby/../libwww-mechanize-ruby1.8/changelog.Debian.gz