Git commits in Moodle 3.6.x by Julien Boulen

commit f8c209cf25e1c3167f75097965c5004e818ac92c
Author: Julien Boulen <julien.boulen@univ-rennes2.fr>
Date:   Mon, 18 Mar 2019 18:18:46 +0800
Tag:    v3.6.4

MDL-46803 course: Prevent unenrol users with multiple roles during reset