public function getPreconditionByHandle($handle)
    {
        $list = $this->config->get('install.preconditions');
        if (!isset($list[$handle])) {
            throw new Exception(sprintf('Unable to find an install precondition with handle %s', $handle));
        }
        if (!$list[$handle]) {
            throw new Exception(sprintf('The precondition with handle %s is disabled', $handle));
        }
        $className = $list[$handle];
        $instance = $this->getPreconditionByClassName($className);

        return $instance;
    }