Developer credits
Git commits in Moodle 3.5.2 by Adrian Perez
commit 10dae695ecc5669ebae9f17e8ecf1fe5150e1720 Author: Adrian Perez <adrian.perez@ffhs.ch> Date: Fri, 20 Jul 2018 20:25:25 +0800 Tag: v3.5.2 MDL-63002 core_grade: fixed deletion of overriden letters