/usr/lib/ruby/vendor_ruby/ is in ruby-mime 0.4.3-1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/mime/
/usr/lib/ruby/vendor_ruby/mime.rb
/usr/lib/ruby/vendor_ruby/mime/composite_media.rb
/usr/lib/ruby/vendor_ruby/mime/content_formats/
/usr/lib/ruby/vendor_ruby/mime/content_formats/text_flowed.rb
/usr/lib/ruby/vendor_ruby/mime/content_types.rb
/usr/lib/ruby/vendor_ruby/mime/discrete_media.rb
/usr/lib/ruby/vendor_ruby/mime/discrete_media_factory.rb
/usr/lib/ruby/vendor_ruby/mime/error.rb
/usr/lib/ruby/vendor_ruby/mime/header.rb
/usr/lib/ruby/vendor_ruby/mime/headers/
/usr/lib/ruby/vendor_ruby/mime/headers/internet.rb
/usr/lib/ruby/vendor_ruby/mime/headers/mime.rb
/usr/lib/ruby/vendor_ruby/mime/mail.rb
/usr/lib/ruby/vendor_ruby/mime/media.rb
/usr/lib/ruby/vendor_ruby/mime/parser.rb