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=98d2e58d19534b0f9cf0faf9ba67c6446040e229
http://github.com/moodle/moodle/commit/98d2e58d19534b0f9cf0faf9ba67c6446040e229
+ 2.1 en [cannotstartgradesmismatch,mod_quiz]