title: Redirect to /admin/login/ results in 302
body: <p>I'm trying to redirect to the login page when a user is not authenticated. In my <code>settings.py</code> class I have:</p>
  
  <pre><code>MIDDLEWARE_CLASSES = [
      'path.to.AuthRequiredMiddleware',
  ]
  </code></pre>
  
  <p>Here is my class:</p>
  
  <pre><code>class AuthRequiredMiddleware(object):
      def process_request(self, request):
          if not request.user.is_authenticated():
              return HttpResponseRedirect('/admin/login/')
          return None
  </code></pre>
  
  <p>However this always results in <code>[24/Jan/2017 14:09:07] "GET /admin/login/ HTTP/1.1" 302 0</code> when the user is not authenticated, does anyone know how to fix this? Changing the redirection URL results in the same issue no matter what it is.</p>
  
  <p>I have also tried to use the <code>django.shortcuts import redirect</code> however I got the same <code>302</code> result as well from it.</p>