title: Passenger could not spawn process for application
body: <p>I have deployed my webapp on CentOS 7 using <code>bundle --standalone</code> and have configured the app to use the correct gems by using <code>.bundle/config</code>.  It works great when I use <code>rails server</code>, but when I <a href="https://www.phusionpassenger.com/library/install/apache/install/oss/el7" rel="nofollow">set it up to use passenger</a> I get the following error:</p>
  
  <pre><code>[ 2016-02-02 13:27:50.7037 5134/7fb8225b8700 age/Cor/App/Implementation.cpp:304 ]: Could not spawn process for application /var/www/rails-web: An error occurred while starting up the preloader. It exited before signalling successful startup back to Phusion Passenger.
    Error ID: 7b0eafb9
    Error details saved to: /tmp/passenger-error-YR2EzW.html
    Message from application: An error occurred while starting up the preloader. It exited before signalling successful startup back to Phusion Passenger. Please read &lt;a href="https://github.com/phusion/passenger/wiki/Debugging-application-startup-problems"&gt;this article&lt;/a&gt; for more information about this problem.&lt;br&gt;
  &lt;h2&gt;Raw process output:&lt;/h2&gt;
  &lt;pre&gt;
  /usr/share/rubygems/rubygems/path_support.rb:68:in `path=&amp;apos;: undefined method `+&amp;apos; for nil:NilClass (NoMethodError)
      from /usr/share/rubygems/rubygems/path_support.rb:30:in `initialize&amp;apos;
      from /usr/share/rubygems/rubygems.rb:357:in `new&amp;apos;
      from /usr/share/rubygems/rubygems.rb:357:in `paths&amp;apos;
      from /usr/share/rubygems/rubygems.rb:379:in `path&amp;apos;
      from /usr/share/rubygems/rubygems/specification.rb:794:in `dirs&amp;apos;
      from /usr/share/rubygems/rubygems/specification.rb:658:in `each_normal&amp;apos;
      from /usr/share/rubygems/rubygems/specification.rb:669:in `_all&amp;apos;
      from /usr/share/rubygems/rubygems/specification.rb:822:in `each&amp;apos;
      from /usr/share/rubygems/rubygems/specification.rb:864:in `find&amp;apos;
      from /usr/share/rubygems/rubygems/specification.rb:864:in `find_inactive_by_path&amp;apos;
      from /usr/share/rubygems/rubygems.rb:175:in `try_activate&amp;apos;
      from /usr/share/rubygems/rubygems/core_ext/kernel_require.rb:132:in `rescue in require&amp;apos;
      from /usr/share/rubygems/rubygems/core_ext/kernel_require.rb:144:in `require&amp;apos;
      from &amp;lt;internal:abrt_prelude&amp;gt;:2:in `&amp;lt;compiled&amp;gt;&amp;apos;
  &lt;/pre&gt;
  </code></pre>
  
  <p>The code around <code>path_support.rb:68</code> involves setting GEM_PATH.  What does this error message mean and how can I fix it.  Thanks.</p>