title: While executing gem, unknown command
body: <p>Whenever I enter a gem command, such as</p>
  
  <pre><code>gem "tilt"
  </code></pre>
  
  <p>or</p>
  
  <pre><code>gem "mysql"
  </code></pre>
  
  <p>I get this error:</p>
  
  <pre><code>While executing gem ... &lt;RuntimeError&gt;
  Unknown command tilt
  </code></pre>
  
  <p>When I run <code>gem list</code>, both tilt and mysql show up on the list, so they are installed. In fact, I get this error with every item on the list. What could be causing this?</p>