Context: server config, virtual host, directory, htaccess
Override: not None
This routine is called to check for any module-specific restrictions placed upon the requested resource.
Where multiple handlers are specified, if any handler in the sequence
returns a value other than
execution of all subsequent handlers for this phase are aborted.
For example, this can be used to restrict access by IP number. To do
so, you would return
HTTP_FORBIDDEN or some such to indicate
that access is not allowed.