ProxySchemeUnknown on Python 3.9

[iwalucas]

During an upgrade from python 3.7 to 3.9 I face an error similar to the one reported on #5297.

The proxies are defined on the system level (export http_proxy and export https_proxy).

It works fine on 3.7.

Expected Result

Requests respect the proxy

Actual Result

Proxy causes the request fo fail

Reproduction Steps

import requests
headers={}
payload={}
url='https://www.someurl.com'
response = requests.request("POST", url, headers=headers, data = payload)

System Information

$ python -m requests.help

{
  "chardet": {
    "version": "3.0.4"
  },
  "cryptography": {
    "version": ""
  },
  "idna": {
    "version": "2.8"
  },
  "implementation": {
    "name": "CPython",
    "version": "3.9.6"
  },
  "platform": {
    "release": "20.6.0",
    "system": "Darwin"
  },
  "pyOpenSSL": {
    "openssl_version": "",
    "version": null
  },
  "requests": {
    "version": "2.22.0"
  },
  "system_ssl": {
    "version": "101010bf"
  },
  "urllib3": {
    "version": "1.25.11"
  },
  "using_pyopenssl": false
}

Traceback

   response = requests.request("POST", url, headers=headers, data = payload)
 File "/usr/local/lib/python3.9/site-packages/requests/api.py", line 60, in request
   return session.request(method=method, url=url, **kwargs)
 File "/usr/local/lib/python3.9/site-packages/requests/sessions.py", line 533, in request
   resp = self.send(prep, **send_kwargs)
 File "/usr/local/lib/python3.9/site-packages/requests/sessions.py", line 646, in send
   r = adapter.send(request, **kwargs)
 File "/usr/local/lib/python3.9/site-packages/requests/adapters.py", line 412, in send
   conn = self.get_connection(request.url, proxies)
 File "/usr/local/lib/python3.9/site-packages/requests/adapters.py", line 309, in get_connection
   proxy_manager = self.proxy_manager_for(proxy)
 File "/usr/local/lib/python3.9/site-packages/requests/adapters.py", line 193, in proxy_manager_for
   manager = self.proxy_manager[proxy] = proxy_from_url(
 File "/usr/local/lib/python3.9/site-packages/urllib3/poolmanager.py", line 492, in proxy_from_url
   return ProxyManager(proxy_url=url, **kw)
 File "/usr/local/lib/python3.9/site-packages/urllib3/poolmanager.py", line 429, in __init__
   raise ProxySchemeUnknown(proxy.scheme)

[nateprewitt]

Hi @iwalucas, can you please provide the proxies you’re using, or at least an identical format with sensitive info substituted? There isn’t enough information to determine if this is the same issue as #5297 or #5855.

In either case, this is almost certainly a duplicate.

[iwalucas]

@nateprewitt I think its a duplicate of #5855...
here are the proxies:

HTTP_PROXY=proxy.mydomain.com:3128
HTTPS_PROXY=proxy.mydomain.com:3128

[nateprewitt]

I've added an update in #5855, we'll track further conversations around this there. I'll resolve this as a duplicate for now. Thanks!