import requests
r = requests.get("https://httpbin.org/ip", proxies={"https":"http://xxx.xxx.xxx.xxx:xxx"}, headers={"User-Agent": "Opera/9.80 (X11; Linux x86_64; U; de) Presto/2.2.15 Version/10.00"})
print(r.json())

requests.exceptions.ProxyError: HTTPSConnectionPool(host='httpbin.org', port=443): Max retries exceeded with url: /ip (Caused by ProxyError('Cannot connect to proxy.', OSError('Tunnel connection failed: 502 Bad Gateway')))