title: Rails 4 Error with every command "`load': no implicit conversion of nil into String" (Mac OS X 10.9)
body: <p>I've just installed a fresh Ruby on Rails dev stack on my new Macbook, which runs Mac OS X 10.9 Mavericks.</p>
  
  <p>Here is my stack:</p>
  
  <ul>
  <li>Xcode command line tools</li>
  <li>Homebrew</li>
  <li>Rbenv</li>
  <li>Bundler</li>
  <li>Ruby 2.1.0</li>
  <li>Rails 4.1.1</li>
  </ul>
  
  <p>I ran <code>rails new test_app</code> to generate a first test app.
  This command successfully completed, but since it, every Rails command I try in my CLI returns this kind of error message:</p>
  
  <pre><code>$ test_app &gt; bin/rails server
  
  /Users/me/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/spring-1.1.3/lib/spring/client/rails.rb:27:in `load': no implicit conversion of nil into String (TypeError)
      from /Users/me/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/spring-1.1.3/lib/spring/client/rails.rb:27:in `call'
      from /Users/me/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/spring-1.1.3/lib/spring/client/command.rb:7:in `call'
      from /Users/me/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/spring-1.1.3/lib/spring/client.rb:26:in `run'
      from /Users/me/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/spring-1.1.3/bin/spring:48:in `&lt;top (required)&gt;'
      from /Users/me/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/spring-1.1.3/lib/spring/binstub.rb:11:in `load'
      from /Users/me/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/spring-1.1.3/lib/spring/binstub.rb:11:in `&lt;top (required)&gt;'
      from /Users/me/.rbenv/versions/2.1.0/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55:in `require'
      from /Users/me/.rbenv/versions/2.1.0/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55:in `require'
      from /Users/me/Documents/[PERSONNEL]/dev/test_app/bin/spring:16:in `&lt;top (required)&gt;'
      from bin/rails:3:in `load'
      from bin/rails:3:in `&lt;main&gt;'
  </code></pre>
  
  <p>Same error while trying to start a console:</p>
  
  <pre><code>$ test_app &gt; bin/rails c
  
  /Users/me/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/activesupport-4.1.1/lib/active_support/dependencies.rb:241:in `load': no implicit conversion of nil into String (TypeError)
      from /Users/me/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/activesupport-4.1.1/lib/active_support/dependencies.rb:241:in `block in load'
      from /Users/me/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/activesupport-4.1.1/lib/active_support/dependencies.rb:232:in `load_dependency'
      from /Users/me/.rbenv/versions/2.1.0/lib/ruby/gems/2.1.0/gems/activesupport-4.1.1/lib/active_support/dependencies.rb:241:in `load'
      from /Users/me/.rbenv/versions/2.1.0/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55:in `require'
      from /Users/me/.rbenv/versions/2.1.0/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55:in `require'
      from -e:1:in `&lt;main&gt;'
  </code></pre>
  
  <p>The <code>bin/rake</code> are working partially (I can use <code>bin/rake routes</code> but migrations are not working).</p>
  
  <p>My last try was to install <strong>XCode</strong>, but it didn't solve it.</p>
  
  <hr>
  
  <p><strong>UPDATE</strong>: the command <code>bundle exec rake rails:update:bin</code> as mentioned bellow solve the problem for project, but needed to be executed on every new problem.
  The problem seems to be deeper.</p>