Fixing Could not open CONNECT tunnel with proxy in Scrapy

import os
import uuid

GATEWAY = "via.proxies.vision:10000"  # the sticky port: it reads a session label


class ResidentialProxyMiddleware:
    """Sets the proxy on every request. meta["country"] picks the exit country,
    meta["session"] keeps one exit for that label; without it, every request
    gets a fresh label and so a new IP, even on a kept-alive connection."""

    def __init__(self):
        self.user = os.environ["PROXY_USER"]
        self.password = os.environ["PROXY_PASS"]

    def process_request(self, request, spider=None):
        if "proxy" in request.meta:
            return None
        user = self.user
        if request.meta.get("country"):
            user += f"-country-{request.meta['country'].lower()}"
        session = request.meta.get("session") or uuid.uuid4().hex[:8]
        user += f"-session-{session}-lifetime-10"
        request.meta["proxy"] = f"http://{user}:{self.password}@{GATEWAY}"
        return None

BOT_NAME = "shop"
SPIDER_MODULES = ["shop.spiders"]

DOWNLOADER_MIDDLEWARES = {
    "shop.middlewares.ResidentialProxyMiddleware": 350,  # before HttpProxyMiddleware (750)
}
# Tunnel errors are retried by default. 403 and 407 won't change on a retry,
# so keep the count low and read the status in the log.
RETRY_TIMES = 1
DOWNLOAD_TIMEOUT = 30

import json

import scrapy


class IpSpider(scrapy.Spider):
    name = "ip"

    async def start(self):
        for i in range(3):  # three requests, three German IPs
            yield scrapy.Request("https://ipinfo.io/json", meta={"country": "de"}, dont_filter=True)
        for i in range(2):  # the same label twice: one IP
            yield scrapy.Request("https://ipinfo.io/json", meta={"country": "de", "session": "account1"}, dont_filter=True)

    def parse(self, response):
        data = json.loads(response.text)
        yield {"session": response.meta.get("session"), "ip": data["ip"], "country": data["country"]}