/usr/lib/ruby/vendor_ruby/ is in ruby-amq-protocol 1.9.2-2.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/amq/
/usr/lib/ruby/vendor_ruby/amq/pack.rb
/usr/lib/ruby/vendor_ruby/amq/protocol.rb
/usr/lib/ruby/vendor_ruby/amq/int_allocator.rb
/usr/lib/ruby/vendor_ruby/amq/uri.rb
/usr/lib/ruby/vendor_ruby/amq/protocol/
/usr/lib/ruby/vendor_ruby/amq/protocol/frame.rb
/usr/lib/ruby/vendor_ruby/amq/protocol/constants.rb
/usr/lib/ruby/vendor_ruby/amq/protocol/table_value_decoder.rb
/usr/lib/ruby/vendor_ruby/amq/protocol/version.rb
/usr/lib/ruby/vendor_ruby/amq/protocol/client.rb
/usr/lib/ruby/vendor_ruby/amq/protocol/table.rb
/usr/lib/ruby/vendor_ruby/amq/protocol/table_value_encoder.rb
/usr/lib/ruby/vendor_ruby/amq/protocol/type_constants.rb
/usr/lib/ruby/vendor_ruby/amq/protocol/exceptions.rb
/usr/lib/ruby/vendor_ruby/amq/protocol/float_32bit.rb
/usr/lib/ruby/vendor_ruby/amq/endianness.rb
/usr/lib/ruby/vendor_ruby/amq/settings.rb
/usr/lib/ruby/vendor_ruby/amq/bit_set.rb