Author: Tim Hunt
MDL-56136 restore: better error handling copying file at start
http://git.moodle.org/gw?p=moodle.git;a=commit;h=493f5d4851de5fbd29262143396943cb33437978
http://github.com/moodle/moodle/commit/493f5d4851de5fbd29262143396943cb33437978
+ 3.1 en [errorcopyingbackupfile,core_backup]