When order_line.status == LINE.FULFILLMENT_TIMEOUT_ERROR, I am not sure whether customer has paid for the course, and whether customer has enrolled to the course.
I am afraid of the scenario that a customer has paid for the course, while not enrolled to the course.
I add `sleep(30)` to common/djangoapps/enrollment/views.py:EnrollmentListView post method, to raise a FULFILLMENT_TIMEOUT_ERROR .