/**
* This method allows the exception to return any extra HTTP response headers.
*
* The headers must be returned as an array.
*
* @return array
*/
public function getHTTPHeaders(Sabre_DAV_Server $server)
{
$methods = $server->getAllowedMethods($server->getRequestUri());
return array('Allow' => strtoupper(implode(', ', $methods)));
}