title: You have already activated rack 1.6.0, but your Gemfile requires rack 1.6.4. Prepending `bundle exec` to your command may solve this. (Gem::LoadError)
body: <p>I'm working with Elastic Beanstalk and I'm getting this error in my logs-</p>
  
  <blockquote>
    <p>You have already activated rack 1.6.0, but your Gemfile requires rack 1.6.4. Prepending <code>bundle exec</code> to your command may solve this. (Gem::LoadError)</p>
  </blockquote>
  
  <p>I've seen all related questions(<a href="https://stackoverflow.com/questions/9241912/how-to-force-rack-to-work-around-the-usual-you-have-already-activated-rack">Related Question</a>) but nothing worked for me.
  When I do <code>gem list | grep rack</code> i get-</p>
  
  <blockquote>
    <p>rack (1.6.4)<br/>
    rack-test (0.6.3)</p>
  </blockquote>
  
  <p>That means I don't have rack(1.6.0) installed, which is confirmed when I do <code>gem uninstall rack -v 1.6.0</code> it gives me-</p>
  
  <blockquote>
    <p>ERROR:  While executing gem ... (Gem::InstallError)
        gem "rack" is not installed</p>
  </blockquote>
  
  <p>What should I do? Should I uninstall rack 1.6.4? (that gives me a warning that I won't have any rack versions)</p>