/usr/lib/ is in ruby-ffi-rzmq 2.0.4-1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/
/usr/lib/ruby/vendor_ruby/
/usr/lib/ruby/vendor_ruby/ffi-rzmq.rb
/usr/lib/ruby/vendor_ruby/ffi-rzmq/
/usr/lib/ruby/vendor_ruby/ffi-rzmq/poll_item.rb
/usr/lib/ruby/vendor_ruby/ffi-rzmq/socket.rb
/usr/lib/ruby/vendor_ruby/ffi-rzmq/context.rb
/usr/lib/ruby/vendor_ruby/ffi-rzmq/poll.rb
/usr/lib/ruby/vendor_ruby/ffi-rzmq/version.rb
/usr/lib/ruby/vendor_ruby/ffi-rzmq/poll_items.rb
/usr/lib/ruby/vendor_ruby/ffi-rzmq/util.rb
/usr/lib/ruby/vendor_ruby/ffi-rzmq/exceptions.rb
/usr/lib/ruby/vendor_ruby/ffi-rzmq/device.rb
/usr/lib/ruby/vendor_ruby/ffi-rzmq/message.rb
/usr/lib/ruby/vendor_ruby/io_extensions.rb