Quiz grades report delete selected attempts conformation doesn't announce itself

Issue
Context changes - When the user clicks the delete selected attempts button the confirmation modal is not announcing that it has appeared to the user.

Standard Level*
WCAG 2 3.3.2 (A) http://www.w3.org/WAI/WCAG20/quickref/#qr-minimize-error-cues

Impact
Serious

Example Link
http://demo.moodle.net/mod/quiz/report.php?id=2461&mode=overview

Test Steps

1. Login as a student
2. navigate to course
3. Click on quiz
4. Click Edit quiz
5. Click the attempts link
6. Select attempts
7. Click the delete selected attempts
8. Notice that the confirmation modal is not announced.