blueberry: print Data as hex, to make matching to wireshark easier

import grpc

import re

from facade import common_pb2 as common

from google.protobuf import text_format

def custom_message_formatter(m, ident, as_one_line):

    if m.DESCRIPTOR == common.Data.DESCRIPTOR:

        return 'payload: (hex) "{}"'.format(m.payload.hex())

    return None

def pretty_print(request):

    return '{} {}'.format(type(request).__name__, text_format.MessageToString(request, as_one_line=True))

    return '{} {}'.format(

        type(request).__name__,

        text_format.MessageToString(request, as_one_line=True, message_formatter=custom_message_formatter))

class LoggingRandezvousWrapper():