title: $GEM is not part of the bundle. Add it to Gemfile
body: <p>Suddenly I can't run rspec or guard anymore. I even did a checkout on an old commit where I know I had some tests running. Same error there.</p>
  
  <pre><code>$ git checkout known-working-commit &amp;&amp; bundle &amp;&amp; rspec spec
  .../ruby-2.2.3@solidus/gems/bundler-1.11.2/lib/bundler/rubygems_integration.rb:304:in 
  `block in replace_gem': rspec-core is not part of the bundle. 
  Add it to Gemfile. (Gem::LoadError)
  </code></pre>
  
  <p>I get the same error if I run <code>rspec</code> and <code>guard</code>.
  Having a look at the PATH exposed by <code>rvm info</code>, I see that guard is available at <code>/Users/martins/.rvm/gems/ruby-2.2.3@solidus/bin/guard</code>. 
  $PATH also has <code>/Users/martins/.rvm/gems/ruby-2.2.3@solidus/bin</code> as it's first entry.
  Any idea what might have gone wrong? I thought that by having a directory listed first in PATH would give it precedence over the other directories listed. How come I get the <code>"bundler-1.11.2/lib/bundler/rubygems_integration.rb:304:in block in replace_gem': rspec-core is not part of the bundle. Add it to Gemfile"</code> error?</p>
  
  <p>I'm running OS X 10.10.5 and ZSH.</p>
  
  <p>My test section from <strong>Gemfile</strong></p>
  
  <pre><code> 19 group :test do
   20   gem 'factory_girl_rails', '~&gt; 4.5.0'
   21   gem 'capybara', '~&gt; 2.4'
   22   gem 'capybara-screenshot'
   23   gem 'database_cleaner', '~&gt; 1.3'
   24   gem 'email_spec'
   25   gem 'launchy'
   26   gem 'rspec-activemodel-mocks', '~&gt;1.0.2'
   27   gem 'rspec-collection_matchers'
   28   gem 'rspec-its'
   29   gem 'rspec-rails', '~&gt; 3.3.0'
   30   gem 'simplecov'
   31   gem 'webmock', '1.8.11'
   32   gem 'poltergeist'
   33   gem 'timecop'
   34   gem 'with_model'
   35   gem 'rspec_junit_formatter'
   36 end
  </code></pre>
  
  <p>The same branch works as expect on my work computer. Which makes me think there is some environment settings that are messing things up.</p>