You can use standard Connecton, as Proxy-Connection is, according to Wiki, Implemented as a misunderstanding of the HTTP specifications. Common because of mistakes in implementations of early HTTP versions. Has exactly the same functionality as standard Connection field. For more details seee the Proxy-Connection: header is a mistake in how some web browsers use HTTP.

But because some clients, curl for instance, send Proxy-Connection some fallback may be needed. Though neither is required by the spec.

Specifically, current implementation doesn't work with aiohttp proxy connector which sends Connection header.

Most asyncio-based libraries and asyncio itself take optional loop argument. Useful for testing as described here.

Return asyncio.Server from start_warp_server so it can later be stopped programmatically. E.g. in tearDown of a test case.

Also returning 1 from start_warp_server in case of the error doesn't make sense (if you didn't really mean sys.exit(1)). So it's better to make it either return asyncio.Server or raise.

    try:
        accept = functools.partial(accept_client, loop=loop)
        yield from asyncio.start_server(accept, host=host, port=port, loop=loop)
    except error as e:
        logger.critical('!!! Fail to bind server at [%s:%d]: %s' % (host, port, e.args[1]))
        return 1
    logger.info('Server bound at [%s:%d].' % (host, port))

NameError: name 'error' is not defined is there because error, obviously, is not a builtin. To catch address-already-in-use OSError should be used.

Header regexes and header name comparisons should be case insensitive because different clients send them in different ways.