Replace this with 
```python
sys_user, __ = User.objects.get_or_create(
    username='system', 
    first_name='System',
)
```
That way you're using the API to manage this. And you don't have to worry about migrations (for the data migration). 
For example, in Django 1.5 a major new feature is the ability to write your own custom User models. So, perhaps when you do that one day you decide to drop the `last_login` field.