Read data from socket *sock*
    Returns None if something went wrong

def read_packet(sock, timeout=None):
    """
    Read data from socket *sock*
    Returns None if something went wrong
    """
    sock.settimeout(timeout)
    dlen, data = None, None
    try:
        if os.name == 'nt':
            #  Windows implementation
            datalen = sock.recv(SZ)
            dlen, = struct.unpack("l", datalen)
            data = b''
            while len(data) < dlen:
                data += sock.recv(dlen)
        else:
            #  Linux/MacOSX implementation
            #  Thanks to eborisch:
            #  See issue 1106
            datalen = temp_fail_retry(socket.error, sock.recv,
                                      SZ, socket.MSG_WAITALL)
            if len(datalen) == SZ:
                dlen, = struct.unpack("l", datalen)
                data = temp_fail_retry(socket.error, sock.recv,
                                       dlen, socket.MSG_WAITALL)
    except socket.timeout:
        raise
    except socket.error:
        data = None
    finally:
        sock.settimeout(None)
    if data is not None:
        try:
            return pickle.loads(data)
        except Exception:
            # Catch all exceptions to avoid locking spyder
            if DEBUG_EDITOR:
                traceback.print_exc(file=STDERR)
            return