/**
* @param object $command
* @param Exception $exception
* @return string|null
*/
public function commandFailed($command, Exception $exception)
{
$exceptionClass = get_class($exception);
$exceptionMessage = $exception->getMessage();
return 'Command failed: ' . get_class($command) . ' ' . $this->serializer->encode($command) . " threw the exception {$exceptionClass} ({$exceptionMessage})";
}