title: is_authenticated returns True for AnonymousUser
body: <p>I am struggling with <code>is_authenticated</code> returning <code>True</code> when I'm not logged in:</p>
  
  <pre><code>u = request.user
  if u.is_authenticated:
      raise Exception('I am said to be authenticated, but I really am not.')
  </code></pre>
  
  <p>To clarify, Django debug view correctly identifies <code>u</code> as an <code>AnonymousUser</code>:</p>
  
  <pre><code>u   &lt;django.contrib.auth.models.AnonymousUser object at 0x9e76f4cc&gt;
  </code></pre>
  
  <p>Even more odd, <strong>inside the template</strong> <code>is_anonymous</code> works fine:</p>
  
  <pre><code>{% if not request.user.is_authenticated %}
      We are anonymous.
  {% endif %}
  </code></pre>
  
  <p>Why is that?</p>