/usr/lib/ruby/vendor_ruby/ is in ruby-fakeredis 0.5.0-1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/fake_redis.rb
/usr/lib/ruby/vendor_ruby/fakeredis/
/usr/lib/ruby/vendor_ruby/fakeredis/version.rb
/usr/lib/ruby/vendor_ruby/fakeredis/expiring_hash.rb
/usr/lib/ruby/vendor_ruby/fakeredis/transaction_commands.rb
/usr/lib/ruby/vendor_ruby/fakeredis/rspec.rb
/usr/lib/ruby/vendor_ruby/fakeredis/sort_method.rb
/usr/lib/ruby/vendor_ruby/fakeredis/command_executor.rb
/usr/lib/ruby/vendor_ruby/fakeredis/sorted_set_store.rb
/usr/lib/ruby/vendor_ruby/fakeredis/zset.rb
/usr/lib/ruby/vendor_ruby/fakeredis/sorted_set_argument_handler.rb
/usr/lib/ruby/vendor_ruby/fakeredis.rb
/usr/lib/ruby/vendor_ruby/redis/
/usr/lib/ruby/vendor_ruby/redis/connection/
/usr/lib/ruby/vendor_ruby/redis/connection/memory.rb