Don't use SubfieldBase as it's not compatible with Django 1.10
Don't use SubfieldBase as it's not compatible with Django 1.10

Use fix used on Wagtail https://github.com/torchbox/wagtail/pull/2736 to avoid
using SubfieldBase for custom fields

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