/usr/lib/ruby/ is in ruby-rails-observers 0.1.1-1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/
/usr/lib/ruby/vendor_ruby/rails/
/usr/lib/ruby/vendor_ruby/rails/observers/
/usr/lib/ruby/vendor_ruby/rails/observers/activerecord/
/usr/lib/ruby/vendor_ruby/rails/observers/activerecord/base.rb
/usr/lib/ruby/vendor_ruby/rails/observers/activerecord/active_record.rb
/usr/lib/ruby/vendor_ruby/rails/observers/activerecord/observer.rb
/usr/lib/ruby/vendor_ruby/rails/observers/version.rb
/usr/lib/ruby/vendor_ruby/rails/observers/active_model/
/usr/lib/ruby/vendor_ruby/rails/observers/active_model/observer_array.rb
/usr/lib/ruby/vendor_ruby/rails/observers/active_model/active_model.rb
/usr/lib/ruby/vendor_ruby/rails/observers/active_model/observing.rb
/usr/lib/ruby/vendor_ruby/rails/observers/action_controller/
/usr/lib/ruby/vendor_ruby/rails/observers/action_controller/caching/
/usr/lib/ruby/vendor_ruby/rails/observers/action_controller/caching/sweeping.rb
/usr/lib/ruby/vendor_ruby/rails/observers/action_controller/caching.rb
/usr/lib/ruby/vendor_ruby/generators/
/usr/lib/ruby/vendor_ruby/generators/test_unit/
/usr/lib/ruby/vendor_ruby/generators/test_unit/observer/
/usr/lib/ruby/vendor_ruby/generators/test_unit/observer/templates/
/usr/lib/ruby/vendor_ruby/generators/test_unit/observer/templates/unit_test.rb
/usr/lib/ruby/vendor_ruby/generators/test_unit/observer/observer_generator.rb
/usr/lib/ruby/vendor_ruby/generators/rails/
/usr/lib/ruby/vendor_ruby/generators/rails/observer/
/usr/lib/ruby/vendor_ruby/generators/rails/observer/USAGE
/usr/lib/ruby/vendor_ruby/generators/rails/observer/observer_generator.rb
/usr/lib/ruby/vendor_ruby/generators/active_record/
/usr/lib/ruby/vendor_ruby/generators/active_record/observer/
/usr/lib/ruby/vendor_ruby/generators/active_record/observer/templates/
/usr/lib/ruby/vendor_ruby/generators/active_record/observer/templates/observer.rb
/usr/lib/ruby/vendor_ruby/generators/active_record/observer/observer_generator.rb
/usr/lib/ruby/vendor_ruby/rails-observers.rb