Author: Amaia Anabitarte
MDL-81503 core_course: Improve section not found error
http://git.moodle.org/gw?p=moodle.git;a=commit;h=0f73bb6cef9c0b930cbb6b7c668c0c3bd4aeaffb
http://github.com/moodle/moodle/commit/0f73bb6cef9c0b930cbb6b7c668c0c3bd4aeaffb
+ 4.5 en [notfound,core_error]
+ 4.5 en [sectioncantbefound,core_error]
+ 4.5 en [gobacktosite,core]