/usr/lib/ruby/ is in ruby-premailer-rails 1.9.7-1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/
/usr/lib/ruby/vendor_ruby/premailer/
/usr/lib/ruby/vendor_ruby/premailer/rails/
/usr/lib/ruby/vendor_ruby/premailer/rails.rb
/usr/lib/ruby/vendor_ruby/premailer/rails/VERSION
/usr/lib/ruby/vendor_ruby/premailer/rails/css_helper.rb
/usr/lib/ruby/vendor_ruby/premailer/rails/css_loaders/
/usr/lib/ruby/vendor_ruby/premailer/rails/css_loaders.rb
/usr/lib/ruby/vendor_ruby/premailer/rails/css_loaders/asset_pipeline_loader.rb
/usr/lib/ruby/vendor_ruby/premailer/rails/css_loaders/cache_loader.rb
/usr/lib/ruby/vendor_ruby/premailer/rails/css_loaders/file_system_loader.rb
/usr/lib/ruby/vendor_ruby/premailer/rails/css_loaders/network_loader.rb
/usr/lib/ruby/vendor_ruby/premailer/rails/customized_premailer.rb
/usr/lib/ruby/vendor_ruby/premailer/rails/hook.rb
/usr/lib/ruby/vendor_ruby/premailer/rails/railtie.rb
/usr/lib/ruby/vendor_ruby/premailer/rails/version.rb