Ruby 2.1.x is EOL (https://www.ruby-lang.org/en/news/2017/04/01/support-of-ruby-2-1-has-ended/)
Ruby 2.1.x is EOL (https://www.ruby-lang.org/en/news/2017/04/01/support-of-ruby-2-1-has-ended/)

appfolio/store_base_sti_class