title: CocoaPods Trunk cannot push update: "You need to register a session first."
body: <p>I am attempting to publish my library using the new <a href="http://blog.cocoapods.org/CocoaPods-Trunk/" rel="noreferrer">CocoaPods Trunk</a> service.</p>
  <pre><code>pod trunk push your-library.podspec
  </code></pre>
  <p>This gives the error:</p>
  <blockquote>
  <p>[!] You need to register a session first.</p>
  </blockquote>
  <p>How does one register a session?</p>