/usr/lib/ruby/vendor_ruby/ is in ruby-omniauth 1.3.1-1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/omniauth.rb
/usr/lib/ruby/vendor_ruby/omniauth/
/usr/lib/ruby/vendor_ruby/omniauth/form.rb
/usr/lib/ruby/vendor_ruby/omniauth/test/
/usr/lib/ruby/vendor_ruby/omniauth/test/strategy_test_case.rb
/usr/lib/ruby/vendor_ruby/omniauth/test/strategy_macros.rb
/usr/lib/ruby/vendor_ruby/omniauth/test/phony_session.rb
/usr/lib/ruby/vendor_ruby/omniauth/strategy.rb
/usr/lib/ruby/vendor_ruby/omniauth/auth_hash.rb
/usr/lib/ruby/vendor_ruby/omniauth/test.rb
/usr/lib/ruby/vendor_ruby/omniauth/builder.rb
/usr/lib/ruby/vendor_ruby/omniauth/failure_endpoint.rb
/usr/lib/ruby/vendor_ruby/omniauth/form.css
/usr/lib/ruby/vendor_ruby/omniauth/strategies/
/usr/lib/ruby/vendor_ruby/omniauth/strategies/developer.rb
/usr/lib/ruby/vendor_ruby/omniauth/version.rb