/usr/lib/ruby/vendor_ruby/ is in ruby-hiredis 0.4.5-2.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/hiredis/
/usr/lib/ruby/vendor_ruby/hiredis/reader.rb
/usr/lib/ruby/vendor_ruby/hiredis/ext/
/usr/lib/ruby/vendor_ruby/hiredis/ext/reader.rb
/usr/lib/ruby/vendor_ruby/hiredis/ext/connection.rb
/usr/lib/ruby/vendor_ruby/hiredis/ruby/
/usr/lib/ruby/vendor_ruby/hiredis/ruby/reader.rb
/usr/lib/ruby/vendor_ruby/hiredis/ruby/connection.rb
/usr/lib/ruby/vendor_ruby/hiredis/connection.rb
/usr/lib/ruby/vendor_ruby/hiredis/version.rb
/usr/lib/ruby/vendor_ruby/1.9.1/
/usr/lib/ruby/vendor_ruby/1.9.1/x86_64-linux/
/usr/lib/ruby/vendor_ruby/1.9.1/x86_64-linux/hiredis/
/usr/lib/ruby/vendor_ruby/1.9.1/x86_64-linux/hiredis/ext/
/usr/lib/ruby/vendor_ruby/1.9.1/x86_64-linux/hiredis/ext/hiredis_ext.so
/usr/lib/ruby/vendor_ruby/hiredis.rb