title: Django - Generate default slug
body: <p>I want to generate a random slug for my model, but without setting "blank=True" (as I want to enforce it later with validation.)</p>
  
  <p>I was wondering if I could do something like this:</p>
  
  <pre><code>slug = models.SlugField(unique=True, default=some_method(), verbose_name='URL Slug')
  </code></pre>
  
  <p>Where some_method is a method which generates a random slug? I've tried the above code and it doesn't work :(</p>
  
  <p>What I'd like to do is generate a unique slug (unique_slugify?)</p>