title: Django model Field default=None useful?
body: <p>In my current project I'm working on we use <code>default=None</code> on model Fields, for <code>models.CharField(default='')</code>. Does this make any sense? I looked into the Django documentation, but couldn't find an answer. I searched the Django source code and for models Field the initial is set to <code>default=NOT_PROVIDED</code> and this is defined as</p>
  <pre class="lang-py prettyprint-override"><code>class NOT_PROVIDED:
      pass
  </code></pre>
  <p>so I'm even more confused now. Running my tests in the Django project I had the feeling, that it does not really matter if I used <code>default=None</code> or <code>default=''</code></p>