title: Django model: NULLable field
body: <p>I'm working on a django project where I need a DateField to sometimes be empty. My model looks like this:</p>
  
  <pre><code>#models.py
  end = models.DateField(default=None, blank=True)
  </code></pre>
  
  <p>But when I run <code>python manage.py sql myapp</code> the sql statement always end up being</p>
  
  <pre><code>CREATE TABLE "myapp_date" (
  "end" date NOT NULL
  );
  </code></pre>
  
  <p>Therefore my field isn't nullable and I can't understand what I should do to make it so. Any idea would be appreciated !</p>