When an assignment description contains an embedded file or a link to a file and that assignment appears in the Calendar block (because it has a due date), the embedded file or link to a file breaks when that course is backed up and restored to a new course.

Steps to reproduce:

1. Create a course.
2. Add an assignment, add a file (e.g., an image) to the description or create a link in the description to an existing resource (e.g., PDF document), and set a due date for the assignment.
3. Add the Calendar block to the course.
4. Backup the course and restore it elsewhere on the site (be sure to include user data).
5. Enroll a user into the restored-to course.
6. As the enrolled user, load the assignment in the restored course. The embedded file or the link work.
7. Still as the enrolled user, go back to the course page and use the Calendar block to click on the due date and then the assignment link.
8. The embedded image or the link in the assignment description here is broken.

Expected result: The files in the description should not be broken. Since the assignment description on the assignment page is correct, the calendar page should also be correct.

Actual result: The assignment page is correct but the calendar page has broken links.