title: How to handle Ruby on Rails error: "Please install the postgresql adapter: `gem install activerecord-postgresql-adapter'"
body: <p>Running a Ruby on Rails (RoR) app or Ruby code which uses the ActiveRecord framework, you get the error message:</p>
  
  <blockquote>
    <p>Please install the postgresql adapter:
    <code>gem install
    activerecord-postgresql-adapter</code></p>
  </blockquote>
  
  <p>Trying to run:</p>
  
  <pre><code>gem install activerecord-postgresql-adapter
  </code></pre>
  
  <p>also fails, leaving you at a loss.</p>