Given how old socket server is, and that it doesn't actually require that API, we should probably just reword the documentation so that it is clear that RequestHandlerClass is the default Handler implementation (and that you can work with setup/handle/finish if you want to subclass it), and document what the *actual* requirements on the Handler are.  

We are unlikely to change socketserver's actual API at this point.

I don't think there's any need for a new issue, let's just make this a documentation issue.  The original title still even applies :)  We will need signoff from someone with more direct interest in the socketserver module than me, but given that the "future" for the stuff socketserver handles is asyncio, I suspect the only objection we might get is "it's not worth it".  But if someone wants to do the work, *I* don't see a reason to reject it.