django 自定义数据校验

http://stackoverflow.com/questions/16231183/django-how-to-override-clean-method-in-a-subclass-of-custom-form

 class SubClassForm(MyCustomForm):
 # ... additional form fields here

 def clean(self):
     # Then call the clean() method of the super  class
     cleaned_data = super(SubClassForm, self).clean()
     # ... do some cross-fields validation for the subclass 

     # Finally, return the cleaned_data
     return cleaned_data