API Gateway のリスポンスヘッダーのカスタマイズ (Python3)

次の記事のプログラムは Node.js で書きましたが、それを Python3 に書き換えました。
API Gateway のリスポンスヘッダーのカスタマイズ (Node.js)

# -*- coding: utf-8 -*-
#
#                   Nov/5/2017
#
# --------------------------------------------------------------------
import sys
import json

# --------------------------------------------------------------------
def py01_handler(event, context):
    sys.stderr.write("*** py01_handler *** start ***\n")
#
    aa = 0
    bb = 0
    cc = 0
#
    sys.stderr.write("Received event.body: " + json.dumps(event) + "\n")
    if ('body' in event):
        json_str = event['body']
        unit_aa = json.loads(json_str)
        if ('aa' in unit_aa):
            sys.stderr.write("aa = " + str(unit_aa['aa']) + "\n")
            aa = int(unit_aa['aa'])
#
        if ('bb' in unit_aa):
            sys.stderr.write("bb = " + str(unit_aa['bb']) + "\n")
            bb = int(unit_aa['bb'])
#
        if ('cc' in unit_aa):
            sys.stderr.write("cc = " + str(unit_aa['cc']) + "\n")
            cc = int(unit_aa['cc'])
#
    version = "Nov/5/2017 PM 20:43"
#
    sum = aa + bb + cc
#
    sys.stderr.write("version = " + version + "\n")
    sys.stderr.write("sum = " + str(sum) + "\n")
    sys.stderr.write("*** py01_handler *** end ***\n")
#
    body = {}
    body['aa'] = aa
    body['bb'] = bb
    body['cc'] = cc
    body['sum'] = sum
    body['version'] = version
    body['language'] = 'Python'
#
    rvalue = {}
    rvalue['statusCode'] = 200
    headers = {}
    headers["X-Custom-Header"] = "Shimotsuke " + version
    headers["X-Powered-By"] = "Python3"
#        headers["Status"] = "200 OK"
    headers["Status"] = "401 Unauthorized"
    rvalue['headers'] = headers
    rvalue['body'] = json.dumps(body)
#
#
    return rvalue
#
# --------------------------------------------------------------------