MDL-36091 added debugging() calls in blocks of code marked as "should never happen"

lib/accesslib.php

@@ -393,6 +393,7 @@ function has_capability($capability, context $context, $user = null, $doanything
     if (!isset($USER->id)) {
         // should never happen
         $USER->id = 0;
+        debugging('Capability check being performed on a user with no ID.', DEBUG_DEVELOPER);
     }
 
     // make sure there is a real user specified
@@ -2062,6 +2063,7 @@ function can_access_course(stdClass $course, $user = null, $withcapability = '',
     if (!isset($USER->id)) {
         // should never happen
         $USER->id = 0;
+        debugging('Course access check being performed on a user with no ID.', DEBUG_DEVELOPER);
     }
 
     // make sure there is a user specified