title: Running "bundle update" tries to install production gems even in development?
body: <p>I'm having a problem running bundle update with mysql2. I don't really need mysql2 in development, and it works in production, so I want to just tell my gemfile the following:</p>
  
  <pre><code>gem 'sqlite3', :group =&gt; :development
  gem 'mysql2', :group =&gt; :production
  </code></pre>
  
  <p>Unfortunately it still says bundle update fails because of mysql2:</p>
  
  <pre><code>An error occurred while installing mysql2 (0.3.14), and Bundler cannot continue.
  Make sure that `gem install mysql2 -v '0.3.14'` succeeds before bundling.
  </code></pre>
  
  <p>Any reason why this is, and what can I do instead?</p>