Author: Eloy Lafuente
MDL-23752 backup - export/import add one missing string
http://git.moodle.org/gw?p=moodle.git;a=commit;h=e7eca65d987d276338329b505512e7c2c8d6e06f
http://github.com/moodle/moodle/commit/e7eca65d987d276338329b505512e7c2c8d6e06f
+ 2.0 en [unknownbackupexporterror,core_error]