We have many issues in the queue pointing out various limitations of drupal_http_request(). A particularly old one, , is basically requiring some government departments and other organizations to run production websites on a hacked core. is working on a robust solution for D8, but that will take a while to settle out. Meanwhile, here's an interim step that can be applied to D8 and D7 that will allow these sites to revert their core hacks, and plug in a contrib solution like httprl, cURL, or some other feature-rich library.
PASSED: [[SimpleTest]]: [MySQL] 190 pass(es). View
FAILED: [[SimpleTest]]: [MySQL] Unable to apply patch drupal-1664784-13-override-core-D7.patch. Unable to apply patch. See the log in the details link for more information. View