/usr/lib/ruby/ is in coquelicot 0.9.2-2.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/
/usr/lib/ruby/vendor_ruby/coquelicot/
/usr/lib/ruby/vendor_ruby/coquelicot.rb
/usr/lib/ruby/vendor_ruby/coquelicot/app.rb
/usr/lib/ruby/vendor_ruby/coquelicot/auth/
/usr/lib/ruby/vendor_ruby/coquelicot/auth.rb
/usr/lib/ruby/vendor_ruby/coquelicot/auth/imap.rb
/usr/lib/ruby/vendor_ruby/coquelicot/auth/simplepass.rb
/usr/lib/ruby/vendor_ruby/coquelicot/base_app.rb
/usr/lib/ruby/vendor_ruby/coquelicot/debian.rb
/usr/lib/ruby/vendor_ruby/coquelicot/depot.rb
/usr/lib/ruby/vendor_ruby/coquelicot/helpers.rb
/usr/lib/ruby/vendor_ruby/coquelicot/jyraphe_migrator.rb
/usr/lib/ruby/vendor_ruby/coquelicot/num.rb
/usr/lib/ruby/vendor_ruby/coquelicot/rack/
/usr/lib/ruby/vendor_ruby/coquelicot/rack/multipart_parser.rb
/usr/lib/ruby/vendor_ruby/coquelicot/rack/upload.rb
/usr/lib/ruby/vendor_ruby/coquelicot/stored_file.rb
/usr/lib/ruby/vendor_ruby/coquelicot/version.rb