def fulfill_course_milestone(course_key, user):
    """
    Marks the course specified by the given course_key as complete for the given user.
    If any other courses require this course as a prerequisite, their milestones will be appropriately updated.
    """
    if not ENABLE_MILESTONES_APP.is_enabled():
        return None
    try:
        course_milestones = milestones_api.get_course_milestones(course_key=course_key, relationship="fulfills")
    except InvalidMilestoneRelationshipTypeException:
        # we have not seeded milestone relationship types
        seed_milestone_relationship_types()
        course_milestones = milestones_api.get_course_milestones(course_key=course_key, relationship="fulfills")
    for milestone in course_milestones:
        milestones_api.add_user_milestone({'id': user.id}, milestone)