title: 'NoneType' object is not callable on Django 2.0
body: <p>I am following <a href="http:///www.obeythetestinggoat.com/book/chapter_working_incrementally.html" rel="nofollow noreferrer">Obeying the Test Goat</a> by HJWP and deploying my Django app on an Ubuntu Droplets and I come across a problem running my functional test (unit tests all clear).</p>
  
  <p>Details: Python 3.6, Django 2.0.1, Selenium, gecko driver 19.1, remote Ubuntu 16.04, local Window 10 git bash</p>
  
  <p>I've been trying to perform a function test both locally and against the server and got the results below:</p>
  
  <p>Local Test Result</p>
  
  <pre><code>File "C:\...\.virtualenvs\superlists\lib\site-
  packages\django\core\handlers\base.py", line 81, in get_response
  response = self._middleware_chain(request)
  TypeError: 'NoneType' object is not callable
  </code></pre>
  
  <p>Against Remote Server Result:</p>
  
  <pre><code>ValueError at /lists/new
  The view lists.views.new_list didn't return an HttpResponse object. It 
  returned None instead.
  Request Method: GET
  Request URL:    http://midsummerseve.life:8000/lists/
  </code></pre>
  
  <p>I think based on the above results, there has to be something wrong with the view function which in this case is</p>
  
  <pre><code>def new_list(request):
      list_ = List.objects.create()
      Item.objects.create(text=request.POST['item_text'], list=list_)
      return redirect(f'/lists/{list_.id}/')
  </code></pre>
  
  <p>But I have no idea where to further and what makes it return a None object.
  Could it be the issue of the models of list and item? Migration steps seem quite smooth though.</p>
  
  <pre><code>class List(models.Model):
  pass
  
  class Item(models.Model):
  text = models.TextField(default='')
  list = models.ForeignKey(List, on_delete=models.CASCADE)
  </code></pre>
  
  <p>I am also wondering why the server would process a GET request as the specific view function would only be called after user hit ENTER sending off a POST request. Another interesting thing is that i could observe that during FT basically everything worked fine and the console gave me 'OK' after several repetitions of the "NoneType" tracebacks.</p>