Author: Daniel Neis Araujo
MDL-48499 messages: Show which users have not received bulk messages
http://git.moodle.org/gw?p=moodle.git;a=commit;h=77acc5d7a7e4a6c1915bd1c265a591a750de23d0
http://github.com/moodle/moodle/commit/77acc5d7a7e4a6c1915bd1c265a591a750de23d0
+ 2.9 en [messagedselecteduserfailed,core]
+ 2.9 en [messagedselectedcountusersfailed,core]