Left a few minor comments in Rietveld.

My only opposition to the RemoteDisconnected error is now we have two exceptions that effectively mean the same thing. It looks like asyncio.streams has similar behaviour: https://hg.python.org/cpython/file/041a27298cf3/Lib/asyncio/streams.py#l193. I think that if it's acceptable to break backwards compatibility here, we should.

Browsing through some Github repos, it seems like this change /could/ potentially impact a few smaller projects. I can confirm, however, that neither urllib3 nor requests are dependent on BadStatusLine.