aiohttp proxy errors: ClientHttpProxyError, SOCKS5 and the environment

import asyncio
import os
from urllib.parse import quote

import aiohttp

USER = os.environ["PROXY_USER"]
PASS = os.environ["PROXY_PASS"]


def proxy_url(targeting: str = "") -> str:
    # quote() keeps @ : / in the password from breaking the URL.
    return f"http://{quote(USER + targeting, safe='')}:{quote(PASS, safe='')}@via.proxies.vision:9000"


async def fetch(url: str, targeting: str = "", attempts: int = 3) -> str:
    for attempt in range(1, attempts + 1):
        # force_close: a new connection per request, so a new exit IP.
        connector = aiohttp.TCPConnector(force_close=True)
        try:
            async with aiohttp.ClientSession(connector=connector, timeout=aiohttp.ClientTimeout(total=30)) as session:
                async with session.get(url, proxy=proxy_url(targeting)) as response:
                    return await response.text()
        except aiohttp.ClientHttpProxyError as err:
            # err.status is the proxy's answer. Don't log str(err): it contains the proxy URL, password included.
            if err.status in (403, 407) or attempt == attempts:
                raise RuntimeError(f"proxy refused with {err.status}") from None
        except aiohttp.ClientError:
            if attempt == attempts:
                raise  # a dropped exit, three times in a row


async def main() -> None:
    ips = await asyncio.gather(*[fetch("https://api.ipify.org", "-country-de") for _ in range(5)])
    print(ips)
    try:
        await fetch("https://api.ipify.org", "-country-usa")
    except RuntimeError as err:
        print(err)


asyncio.run(main())