title: Error while installing rack
body: <p>I am getting the following error while installing rack</p>
  
  <p>❯ sudo -E gem install rack -v '2.0.0.alpha'</p>
  
  <blockquote>
    <p>ERROR:  Error installing rack:    rack requires Ruby version >= 2.2.2.</p>
  </blockquote>
  
  <p>The output of the ruby -v gives</p>
  
  <blockquote>
    <p>ruby 2.3.0p0 (2015-12-25 revision 53290) [x86_64-linux-gnu]</p>
  </blockquote>
  
  <p>The output of gem -v gives</p>
  
  <blockquote>
    <p>2.5.1</p>
  </blockquote>
  
  <p>How can i fix this error?</p>