Unknown HTTP status code handling

[rkben]

Currently httpx.RemoteProtocolError is raised when an unknown status code is returned. Should this be raised at all for status codes > 600?
I assume the common paradigm is to check for a specific status code(s) then fall through otherwise. I would propose this should not raise at all but given a default value of "Unknown" or similar. At the least raise with something a bit more verbose such as UnknownStatusCode.

This came up with linkedin, which returns 999 (because of course they do).

import httpx
a = httpx.get("https://www.linkedin.com/in/abc/")

[lovelydinosaur]

Thanks for noting this @rkben. We're moving to have more relaxed handling here.

This pull request on h11 resolves the issue - python-hyper/h11#140
Once that's merged and released then the behaviour will be to not raise an error on that case.