Author: Tim Hunt
MDL-31702 quiz: clarify error message that has been confusing people.
http://git.moodle.org/gw?p=moodle.git;a=commit;h=53e40ebe2d7f89e3480628ae00de462c97df7556
http://github.com/moodle/moodle/commit/53e40ebe2d7f89e3480628ae00de462c97df7556
+ 2.2 en [cannotstartgradesmismatch,mod_quiz]