Author: Eloy Lafuente (stronk7)
MDL-63421 env: Moodle 3.4.x and 3.5.x do not support PHP 7.3
http://git.moodle.org/gw?p=moodle.git;a=commit;h=8a95de6bccd5e3ce1cd97134a63dabdf33c65960
http://github.com/moodle/moodle/commit/8a95de6bccd5e3ce1cd97134a63dabdf33c65960
+ 3.6 en [unsupportedphpversion73,core_admin]