def coerce(cls, string):
        """Create a :class:`Requirement` object from a given package spec."""
        match = re.match(cls.spec_regex, string)
        if not match:
            raise InvalidRequirementSpecError("could not parse requirement")
        package = match.group(1)
        if all(match.group(2, 3)):
            version = "".join(match.group(2, 3))
        else:
            version = None
        return cls(package, version)
async def echo_client(loop, client):
    try:
        client.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)
    except (OSError, NameError):
        pass

    with client:
        while True:
            data = await loop.sock_recv(client, 1000000)
            if not data:
                break
            await loop.sock_sendall(client, data)
    if PRINT:
        print('Connection closed')