0. Go to the reports for a quiz with attempts (Quiz -> Results in the navgation block).
1. Try Regrade all in the Grades report
2. Try to delete an attempt in the Grades report.
3. Try to delete an attempt in the responses report.
See http://tracker.moodle.org/browse/MDL-3030?focusedCommentId=155327&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-155327
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