Class: qbehaviour_missing - X-Ref
Fake question behaviour that is used when the actual behaviour
is not available.
Imagine, for example, that a quiz attempt has been restored from another
Moodle site with more behaviours installed, or a behaviour
that used to be available in this site has been uninstalled. Obviously all we
can do is have some code to prevent fatal errors.
The approach we take is: The rendering code is still implemented, as far as
possible. A warning is shown that behaviour specific bits may be missing.
Any attempt to process anything causes an exception to be thrown.