private function makeFile()
{
$url = $this->fileUrl();
$body = implode(',', $this->contexts);
$response = $this->post($url, $body);
if ($response->needRetry()) {
$response = $this->post($url, $body);
}
if (!$response->ok()) {
return array(null, new Error($this->currentUrl, $response));
}
return array($response->json(), null);
}