/usr/lib/ruby/ is in ruby-celluloid-io 0.16.2-5.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/
/usr/lib/ruby/vendor_ruby/celluloid/
/usr/lib/ruby/vendor_ruby/celluloid/io/
/usr/lib/ruby/vendor_ruby/celluloid/io/dns_resolver.rb
/usr/lib/ruby/vendor_ruby/celluloid/io/mailbox.rb
/usr/lib/ruby/vendor_ruby/celluloid/io/reactor.rb
/usr/lib/ruby/vendor_ruby/celluloid/io/ssl_server.rb
/usr/lib/ruby/vendor_ruby/celluloid/io/ssl_socket.rb
/usr/lib/ruby/vendor_ruby/celluloid/io/stream.rb
/usr/lib/ruby/vendor_ruby/celluloid/io/tcp_server.rb
/usr/lib/ruby/vendor_ruby/celluloid/io/tcp_socket.rb
/usr/lib/ruby/vendor_ruby/celluloid/io/udp_socket.rb
/usr/lib/ruby/vendor_ruby/celluloid/io/unix_server.rb
/usr/lib/ruby/vendor_ruby/celluloid/io/unix_socket.rb
/usr/lib/ruby/vendor_ruby/celluloid/io/version.rb
/usr/lib/ruby/vendor_ruby/celluloid/io.rb