/usr/lib/ruby/ is in ruby-rspec-core 2.5.1-1ubuntu2.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/
/usr/lib/ruby/vendor_ruby/autotest/
/usr/lib/ruby/vendor_ruby/autotest/discover.rb
/usr/lib/ruby/vendor_ruby/autotest/rspec2.rb
/usr/lib/ruby/vendor_ruby/rspec/
/usr/lib/ruby/vendor_ruby/rspec/monkey/
/usr/lib/ruby/vendor_ruby/rspec/monkey/spork/
/usr/lib/ruby/vendor_ruby/rspec/monkey/spork/test_framework/
/usr/lib/ruby/vendor_ruby/rspec/monkey/spork/test_framework/rspec.rb
/usr/lib/ruby/vendor_ruby/rspec/autorun.rb
/usr/lib/ruby/vendor_ruby/rspec/core/
/usr/lib/ruby/vendor_ruby/rspec/core/configuration.rb
/usr/lib/ruby/vendor_ruby/rspec/core/option_parser.rb
/usr/lib/ruby/vendor_ruby/rspec/core/configuration_options.rb
/usr/lib/ruby/vendor_ruby/rspec/core/extensions/
/usr/lib/ruby/vendor_ruby/rspec/core/extensions/instance_eval_with_args.rb
/usr/lib/ruby/vendor_ruby/rspec/core/extensions/object.rb
/usr/lib/ruby/vendor_ruby/rspec/core/extensions/module_eval_with_args.rb
/usr/lib/ruby/vendor_ruby/rspec/core/extensions/kernel.rb
/usr/lib/ruby/vendor_ruby/rspec/core/reporter.rb
/usr/lib/ruby/vendor_ruby/rspec/core/example.rb
/usr/lib/ruby/vendor_ruby/rspec/core/errors.rb
/usr/lib/ruby/vendor_ruby/rspec/core/version.rb
/usr/lib/ruby/vendor_ruby/rspec/core/subject.rb
/usr/lib/ruby/vendor_ruby/rspec/core/runner.rb
/usr/lib/ruby/vendor_ruby/rspec/core/example_group.rb
/usr/lib/ruby/vendor_ruby/rspec/core/let.rb
/usr/lib/ruby/vendor_ruby/rspec/core/command_line.rb
/usr/lib/ruby/vendor_ruby/rspec/core/ruby_project.rb
/usr/lib/ruby/vendor_ruby/rspec/core/deprecation.rb
/usr/lib/ruby/vendor_ruby/rspec/core/metadata.rb
/usr/lib/ruby/vendor_ruby/rspec/core/backward_compatibility.rb
/usr/lib/ruby/vendor_ruby/rspec/core/extensions.rb
/usr/lib/ruby/vendor_ruby/rspec/core/drb_command_line.rb
/usr/lib/ruby/vendor_ruby/rspec/core/rake_task.rb
/usr/lib/ruby/vendor_ruby/rspec/core/hooks.rb
/usr/lib/ruby/vendor_ruby/rspec/core/pending.rb
/usr/lib/ruby/vendor_ruby/rspec/core/command_line_configuration.rb
/usr/lib/ruby/vendor_ruby/rspec/core/load_path.rb
/usr/lib/ruby/vendor_ruby/rspec/core/shared_context.rb
/usr/lib/ruby/vendor_ruby/rspec/core/mocking/
/usr/lib/ruby/vendor_ruby/rspec/core/mocking/with_mocha.rb
/usr/lib/ruby/vendor_ruby/rspec/core/mocking/with_rspec.rb
/usr/lib/ruby/vendor_ruby/rspec/core/mocking/with_flexmock.rb
/usr/lib/ruby/vendor_ruby/rspec/core/mocking/with_absolutely_nothing.rb
/usr/lib/ruby/vendor_ruby/rspec/core/mocking/with_rr.rb
/usr/lib/ruby/vendor_ruby/rspec/core/shared_example_group.rb
/usr/lib/ruby/vendor_ruby/rspec/core/world.rb
/usr/lib/ruby/vendor_ruby/rspec/core/expecting/
/usr/lib/ruby/vendor_ruby/rspec/core/expecting/with_rspec.rb
/usr/lib/ruby/vendor_ruby/rspec/core/expecting/with_stdlib.rb
/usr/lib/ruby/vendor_ruby/rspec/core/formatters/
/usr/lib/ruby/vendor_ruby/rspec/core/formatters/base_text_formatter.rb
/usr/lib/ruby/vendor_ruby/rspec/core/formatters/base_formatter.rb
/usr/lib/ruby/vendor_ruby/rspec/core/formatters/text_mate_formatter.rb
/usr/lib/ruby/vendor_ruby/rspec/core/formatters/html_formatter.rb
/usr/lib/ruby/vendor_ruby/rspec/core/formatters/documentation_formatter.rb
/usr/lib/ruby/vendor_ruby/rspec/core/formatters/snippet_extractor.rb
/usr/lib/ruby/vendor_ruby/rspec/core/formatters/progress_formatter.rb
/usr/lib/ruby/vendor_ruby/rspec/core/formatters/helpers.rb
/usr/lib/ruby/vendor_ruby/rspec/core.rb
/usr/lib/ruby/vendor_ruby/rspec/monkey.rb