right now, you can only use course_title, course_code, or offering_id to modify courses.

If you have more than one course with a given course_code, you get the message below.

I'll admit that it's unusual to reuse a course_code,  but this could be easily fixed by allowing an update by "course_id", which [I presume] is absolutely unique.

This would further make this import more consistent with others.