fix for MDL-9016, clearing context cache after remove_course_content()

lib/accesslib.php

@@ -1521,6 +1521,15 @@ function get_context_instance($contextlevel=NULL, $instance=SITEID) {
     if ($contextlevel == CONTEXT_COURSE && $instance == SITEID) {
         $contextlevel = CONTEXT_SYSTEM;
     }
+    
+    // fix for MDL-9016
+    if ($contextlevel == 'clearcache') {
+        // Clear ALL cache
+        $context_cache = array();
+        $context_cache_id = array();
+        $CONTEXT = '';       
+        return false;
+    }
 
 /// If no level is supplied then return the current global context if there is one
     if (empty($contextlevel)) {

lib/moodlelib.php

@@ -2871,7 +2871,12 @@ function remove_course_contents($courseid, $showfeedback=true) {
     if ($courseid != SITEID) {
         delete_context(CONTEXT_COURSE, $course->id);
     }
-
+    
+    // fix for MDL-9016
+    // clear the cache because the course context is deleted, and
+    // we don't want to write assignment, overrides and context_rel table
+    // with this old context id!
+    get_context_instance('clearcache');
     return $result;
 }