def urlopen(self, method, url, redirect=True, **kw):
        "Same as HTTP(S)ConnectionPool.urlopen, ``url`` must be absolute."
        u = parse_url(url)

        if u.scheme == "http":
            # For proxied HTTPS requests, httplib sets the necessary headers
            # on the CONNECT to the proxy. For HTTP, we'll definitely
            # need to set 'Host' at the very least.
            headers = kw.get("headers", self.headers)
            kw["headers"] = self._set_proxy_headers(url, headers)

        return super(ProxyManager, self).urlopen(method, url, redirect=redirect, **kw)
Same as HTTP(S)ConnectionPool.urlopen, ``url`` must be absolute.
product/gradle-plugin/src/main/python/pip/_vendor/urllib3/poolmanager.py