title: An error occurred while installing pg (1.2.1), and Bundler cannot continue
body: <p>I am using CentOS 6 and during bundle install, I get this error.</p>
  <pre><code>An error occurred while installing pg (1.2.1), and Bundler cannot continue.
  Make sure that `gem install pg -v '1.2.1' --source 'https://rubygems.org/'` succeeds before bundling.
  </code></pre>
  <p>I tried this</p>
  <pre><code>gem install pg -v '1.2.1' --source 'https://rubygems.org/'
  </code></pre>
  <p>and</p>
  <pre><code>sudo yum install libpq-dev
  </code></pre>