/usr/lib/ruby/vendor_ruby/ is in ruby-flexmock 0.9.0-1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/flexmock.rb
/usr/lib/ruby/vendor_ruby/flexmock/
/usr/lib/ruby/vendor_ruby/flexmock/version.rb
/usr/lib/ruby/vendor_ruby/flexmock/validators.rb
/usr/lib/ruby/vendor_ruby/flexmock/undefined.rb
/usr/lib/ruby/vendor_ruby/flexmock/test_unit_integration.rb
/usr/lib/ruby/vendor_ruby/flexmock/test_unit.rb
/usr/lib/ruby/vendor_ruby/flexmock/rspec.rb
/usr/lib/ruby/vendor_ruby/flexmock/recorder.rb
/usr/lib/ruby/vendor_ruby/flexmock/rails.rb
/usr/lib/ruby/vendor_ruby/flexmock/rails/
/usr/lib/ruby/vendor_ruby/flexmock/rails/view_mocking.rb
/usr/lib/ruby/vendor_ruby/flexmock/partial_mock.rb
/usr/lib/ruby/vendor_ruby/flexmock/ordering.rb
/usr/lib/ruby/vendor_ruby/flexmock/noop.rb
/usr/lib/ruby/vendor_ruby/flexmock/mock_container.rb
/usr/lib/ruby/vendor_ruby/flexmock/expectation_director.rb
/usr/lib/ruby/vendor_ruby/flexmock/expectation.rb
/usr/lib/ruby/vendor_ruby/flexmock/errors.rb
/usr/lib/ruby/vendor_ruby/flexmock/deprecated_methods.rb
/usr/lib/ruby/vendor_ruby/flexmock/default_framework_adapter.rb
/usr/lib/ruby/vendor_ruby/flexmock/core_class_methods.rb
/usr/lib/ruby/vendor_ruby/flexmock/core.rb
/usr/lib/ruby/vendor_ruby/flexmock/composite.rb
/usr/lib/ruby/vendor_ruby/flexmock/base.rb
/usr/lib/ruby/vendor_ruby/flexmock/argument_types.rb
/usr/lib/ruby/vendor_ruby/flexmock/argument_matchers.rb