/usr/lib/ruby/ is in ruby-celluloid-essentials 0.20.5-1.
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/internals/
/usr/lib/ruby/vendor_ruby/celluloid/internals/registry.rb
/usr/lib/ruby/vendor_ruby/celluloid/internals/properties.rb
/usr/lib/ruby/vendor_ruby/celluloid/internals/cpu_counter.rb
/usr/lib/ruby/vendor_ruby/celluloid/internals/signals.rb
/usr/lib/ruby/vendor_ruby/celluloid/internals/logger.rb
/usr/lib/ruby/vendor_ruby/celluloid/internals/stack.rb
/usr/lib/ruby/vendor_ruby/celluloid/internals/handlers.rb
/usr/lib/ruby/vendor_ruby/celluloid/internals/method.rb
/usr/lib/ruby/vendor_ruby/celluloid/internals/call_chain.rb
/usr/lib/ruby/vendor_ruby/celluloid/internals/thread_handle.rb
/usr/lib/ruby/vendor_ruby/celluloid/internals/receivers.rb
/usr/lib/ruby/vendor_ruby/celluloid/internals/task_set.rb
/usr/lib/ruby/vendor_ruby/celluloid/internals/stack/
/usr/lib/ruby/vendor_ruby/celluloid/internals/stack/summary.rb
/usr/lib/ruby/vendor_ruby/celluloid/internals/stack/dump.rb
/usr/lib/ruby/vendor_ruby/celluloid/internals/stack/states.rb
/usr/lib/ruby/vendor_ruby/celluloid/internals/links.rb
/usr/lib/ruby/vendor_ruby/celluloid/internals/uuid.rb
/usr/lib/ruby/vendor_ruby/celluloid/internals/responses.rb
/usr/lib/ruby/vendor_ruby/celluloid/logger.rb
/usr/lib/ruby/vendor_ruby/celluloid/notifications.rb
/usr/lib/ruby/vendor_ruby/celluloid/essentials.rb
/usr/lib/ruby/vendor_ruby/celluloid/probe.rb
/usr/lib/ruby/vendor_ruby/celluloid/logging/
/usr/lib/ruby/vendor_ruby/celluloid/logging/incident.rb
/usr/lib/ruby/vendor_ruby/celluloid/logging/incident_reporter.rb
/usr/lib/ruby/vendor_ruby/celluloid/logging/log_event.rb
/usr/lib/ruby/vendor_ruby/celluloid/logging/ring_buffer.rb
/usr/lib/ruby/vendor_ruby/celluloid/logging/incident_logger.rb