/usr/lib/ruby/vendor_ruby/ is in ruby-websocket-driver 0.6.3-2.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/websocket/
/usr/lib/ruby/vendor_ruby/websocket/driver.rb
/usr/lib/ruby/vendor_ruby/websocket/http.rb
/usr/lib/ruby/vendor_ruby/websocket/driver/
/usr/lib/ruby/vendor_ruby/websocket/driver/proxy.rb
/usr/lib/ruby/vendor_ruby/websocket/driver/headers.rb
/usr/lib/ruby/vendor_ruby/websocket/driver/client.rb
/usr/lib/ruby/vendor_ruby/websocket/driver/event_emitter.rb
/usr/lib/ruby/vendor_ruby/websocket/driver/hybi.rb
/usr/lib/ruby/vendor_ruby/websocket/driver/hybi/
/usr/lib/ruby/vendor_ruby/websocket/driver/hybi/frame.rb
/usr/lib/ruby/vendor_ruby/websocket/driver/hybi/message.rb
/usr/lib/ruby/vendor_ruby/websocket/driver/stream_reader.rb
/usr/lib/ruby/vendor_ruby/websocket/driver/draft75.rb
/usr/lib/ruby/vendor_ruby/websocket/driver/utf8_match.rb
/usr/lib/ruby/vendor_ruby/websocket/driver/draft76.rb
/usr/lib/ruby/vendor_ruby/websocket/driver/server.rb
/usr/lib/ruby/vendor_ruby/websocket/http/
/usr/lib/ruby/vendor_ruby/websocket/http/headers.rb
/usr/lib/ruby/vendor_ruby/websocket/http/request.rb
/usr/lib/ruby/vendor_ruby/websocket/http/response.rb
/usr/lib/ruby/vendor_ruby/websocket/websocket_mask.rb