/usr/lib/ruby/vendor_ruby/ is in ruby-spy 0.4.3-1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/spy/
/usr/lib/ruby/vendor_ruby/spy/agency.rb
/usr/lib/ruby/vendor_ruby/spy/api.rb
/usr/lib/ruby/vendor_ruby/spy/base.rb
/usr/lib/ruby/vendor_ruby/spy/call_log.rb
/usr/lib/ruby/vendor_ruby/spy/constant.rb
/usr/lib/ruby/vendor_ruby/spy/core_ext/
/usr/lib/ruby/vendor_ruby/spy/core_ext/marshal.rb
/usr/lib/ruby/vendor_ruby/spy/exceptions.rb
/usr/lib/ruby/vendor_ruby/spy/integration.rb
/usr/lib/ruby/vendor_ruby/spy/mock.rb
/usr/lib/ruby/vendor_ruby/spy/nest.rb
/usr/lib/ruby/vendor_ruby/spy/subroutine.rb
/usr/lib/ruby/vendor_ruby/spy/version.rb
/usr/lib/ruby/vendor_ruby/spy.rb