Author: Mark Nelson
MDL-65093 core_message: users can't block any user they want
If blocking will have no effect (ie. you are attempting to block
the admin) the 'Block' button will not be shown and instead a
message will be shown explaining why you can not block the user.
http://git.moodle.org/gw?p=moodle.git;a=commit;h=90403c5d9decd165b88d5cfd1903849f9a60555e
http://github.com/moodle/moodle/commit/90403c5d9decd165b88d5cfd1903849f9a60555e
+ 3.8 en [cantblockuser,core_message]