Stanford-Online/class2go — pull request #876 by jbau (2012-09-28 08:59:51+00:00)
Title: Broaden the search for matching student ProblemActivity #875

instead of an id matching a current ProblemSetToExercise in the set. This is because new ProblemSetToExercise entries for existing exercise files get
created at unexpected times, such as when any exercise is added or deleted in the problem set.