Author: Petr Škoda
MDL-34441 improve error handling when migrating databases
http://git.moodle.org/gw?p=moodle.git;a=commit;h=3ce26ee7f468d7a738c790fd0825a9678b3cf54d
http://github.com/moodle/moodle/commit/3ce26ee7f468d7a738c790fd0825a9678b3cf54d
+ 2.4 en [targetdatabasenotempty,tool_dbtransfer]