The retry logic and code used by ProxyBasicAuthHandler and ProxyDigestAuthHandler are same as normal authentication handlers. While this reuse is good, there is a problem that, on authentication failure, the HTTPError code is hardcoded to 401, whereas for Proxy cases it should have been 407.

The problematic line is this:


    def http_error_auth_reqed(self, auth_header, host, req, headers):
            ...
            raise HTTPError(req.full_url, 401, "digest auth failed",
                            headers, None)

can be changed by:
- Passing the errcode as arg.
- Or getting it from headers.