title: Using South to convert ForeignKey TO ManyToManyField not working out
body: <p>I am using South to change a ForeignKey TO ManyToManyField in one of the models in Django but it is not working out as expected.</p>
  
  <pre><code># Original Schema
  class Item(models.Model):
      category = models.ForeignKey(Category, default=default_category)
  </code></pre>
  
  <p>To be changed to </p>
  
  <pre><code># Original Schema
  class Item(models.Model):
      category = models.ManyToManyField(Category, default=default_category)
  </code></pre>
  
  <p>So after commenting out the ForeignKey line in the model I do,</p>
  
  <pre><code>python manage.py schemamigration affected_model --auto
   ? The field 'Item.category' does not have a default specified, yet is NOT NULL.
   ? Since you are removing this field, you MUST specify a default
   ? value to use for existing rows. Would you like to:
   ?  1. Quit now, and add a default to the field in models.py
   ?  2. Specify a one-off value to use for existing columns now
   ?  3. Disable the backwards migration by raising an exception.
   ? Please select a choice: 
  </code></pre>
  
  <p>I am confused by this because 1. I have specified a default value which is "default_category" and 2. I am not removing any field I am just changing it to ManyToManyField. My question is how to go ahead in this case? Is there any other trick to make this conversion using South?</p>
  
  <p>BTW I am using South 0.7 and Django 1.1.1 </p>
  
  <p>Thanks for the help.</p>