private function buildUri($uri, array $config)
{
// for BC we accept null which would otherwise fail in uri_for
$uri = Psr7\uri_for($uri === null ? '' : $uri);
if (isset($config['base_uri'])) {
$uri = Psr7\Uri::resolve(Psr7\uri_for($config['base_uri']), $uri);
}
return $uri->getScheme() === '' ? $uri->withScheme('http') : $uri;
}