Make it clear the import requires a courseshortname

classes/import/sessions.php

@@ -92,7 +92,7 @@ class sessions {
      */
     public static function list_required_headers() {
         return array(
-            get_string('course', 'attendance'),
+            get_string('courseshortname', 'attendance'),
             get_string('groups', 'attendance'),
             get_string('sessiondate', 'attendance'),
             get_string('from', 'attendance'),

lang/en/attendance.php

@@ -106,6 +106,7 @@ $string['confirmdeleteuser'] = 'Are you sure you want to delete user \'{$a->full
 $string['copyfrom'] = 'Copy attendance data from';
 $string['countofselected'] = 'Count of selected';
 $string['course'] = 'Course';
+$string['courseshortname'] = 'Course shortname';
 $string['coursesummary'] = 'Course summary report';
 $string['createmultiplesessions'] = 'Create multiple sessions';
 $string['createmultiplesessions_help'] = 'This function allows you to create multiple sessions in one simple step.