Fixed #11162 -- Mentioned ValidationError in custom model field docs

            p1 = re.compile('.{26}')

            p2 = re.compile('..')

            args = [p2.findall(x) for x in p1.findall(value)]

            if len(args) != 4:

                raise ValidationError("Invalid input for a Hand instance")

            return Hand(*args)

Notice that we always return a ``Hand`` instance from this method. That's the

Python object type we want to store in the model's attribute.

Python object type we want to store in the model's attribute. If anything is

going wrong during value conversion, you should return a

:exc:`~django.core.exceptions.ValidationError` exception.

**Remember:** If your custom field needs the :meth:`to_python` method to be

called when it is created, you should be using `The SubfieldBase metaclass`_