title: South migrate error: name 'UUID' is not defined
body: <p>I have a model with a CharField field with a default value of uuid4:</p>
  
  <pre><code>f = models.CharField(default=uuid4, max_length=36, unique=True, blank=True)
  </code></pre>
  
  <p>and this is causing the following error:</p>
  
  <blockquote>
    <p>Cannot successfully create field 'f' for model
    'm': name 'UUID' is not defined.</p>
  </blockquote>
  
  <p>running the migrate commmand! Ho can I fix this issue? so far I tried:</p>
  
  <ul>
  <li>to define a "wrapper function" in the module for uuid (ie: def getUUID())</li>
  <li>to set the default value of "f" by overriding the Model constructor</li>
  </ul>
  
  <p>...but the problem remains :(</p>
  
  <p>ps. I know that I can instruct south for custom fields, but I'm not using custom fields in my opinion :P</p>