'Configure the verification deadline for a course.
If `deadline` is `None`, then the course will have no verification
deadline.  In this case, users will be able to verify for the course
at any time.
Arguments:
course_key (CourseKey): Identifier for the course.
deadline (datetime or None): The verification deadline.'

@classmethod
def set_deadline(cls, course_key, deadline, is_explicit=False):

    if (deadline is None):
        VerificationDeadline.objects.filter(course_key=course_key).delete()
    else:
        (record, created) = VerificationDeadline.objects.get_or_create(course_key=course_key, defaults={'deadline': deadline, 'deadline_is_explicit': is_explicit})
        if (not created):
            record.deadline = deadline
            record.deadline_is_explicit = is_explicit
            record.save()
