Author: Andrew Davis
MDL-32913 core_grade:made it more obvious when the gradebook is broken due to a broken calculation
http://git.moodle.org/gw?p=moodle.git;a=commit;h=0f60e9fe539e6fe3e88b5edec5e15c2931697cfa
http://github.com/moodle/moodle/commit/0f60e9fe539e6fe3e88b5edec5e15c2931697cfa
+ 2.4 en [gradecantregrade,core_error]
+ 2.4 en [errorcalculationbroken,core_grades]