Explain that None is a possible value
Explain that None is a possible value

django-oscar/django-oscar,sasha0/django-oscar,solarissmoke/django-oscar,django-oscar/django-oscar,sasha0/django-oscar,solarissmoke/django-oscar,solarissmoke/django-oscar,sasha0/django-oscar,django-oscar/django-oscar,django-oscar/django-oscar,solarissmoke/django-oscar,sasha0/django-oscar