websocket.__init__(): record the handler (for passing user/config info down)
websocket.read_thread(): catch ClosedError

backdoor.print_result(): override to print the result specially (e.g., pprint)

init close_it

since h76 reads delimited data, use request.client.stream for both protocols (a good idea anyway)

HTTP_Upgrade: new exception

The previous content was confusing, outdated, and unhelpful.

Thanks, the fix looks good. I forgot to port notify_on_close to linux during the process.  

read_thread(): catch exit sentinel
request.close(): push exit sentinel
response_re, _read_message(): collect 'reason' (though it's useless)
_read_message(): use req.has_body()
send_request(): pass in extra args to request() constructor

HTTP_Protocol_Error: forgot to move this from server.py
http_file.__init__(), http_file._gen_read_all() : handle the old-school situation where data goes until "connection: close"

added: enum for FLUSH values

header_set.__delitem__(): remove a header
header_set.copy(): copy a header set

Bad_Response: new exception