How to use the portend.Timeout function in portend

@contextlib.contextmanager
def _safe_wait(host, port):
    """
    On systems where a loopback interface is not available and the
    server is bound to all interfaces, it's difficult to determine
    whether the server is in fact occupying the port. In this case,
    just issue a warning and move on. See issue #1100.
    """
    try:
        yield
    except portend.Timeout:
        if host == portend.client_host(host):
            raise
        msg = 'Unable to verify that the server is bound on %r' % port
        warnings.warn(msg)

def check_port_availability(host, port):
    """
    Make sure the port is available for the server to start.
    """
    try:
        portend.free(host, port, timeout=PORT_AVAILABILITY_CHECK_TIMEOUT)
    except portend.Timeout:
        # Bypass check when socket activation is used
        # https://manpages.debian.org/testing/libsystemd-dev/sd_listen_fds.3.en.html#ENVIRONMENT
        if not os.environ.get("LISTEN_PID", None):
            # Port is occupied
            logger.error(
                "Port {} is occupied.\n"
                "Please check that you do not have other processes "
                "running on this port and try again.\n".format(port)
            )
            sys.exit(1)

def _safe_wait(host, port):
    """
    On systems where a loopback interface is not available and the
    server is bound to all interfaces, it's difficult to determine
    whether the server is in fact occupying the port. In this case,
    just issue a warning and move on. See issue #1100.
    """
    try:
        yield
    except portend.Timeout:
        if host == portend.client_host(host):
            raise
        msg = 'Unable to verify that the server is bound on %r' % port
        warnings.warn(msg)