DjangoとHerokuでLINEbotを製作中 callbackが上手くいかない

前提・実現したいこと

PythonでDjangoとHerokuを使ってLINEbotを製作しています。

https://qiita.com/yakan10/items/b7ad35c2cbba5db81462

こちらを参考に似たものを作っているのですが、実際に最後まで作って見たところcallbackの処理が上手くいっていないようです。原因がいまいち分からないので良ければ教えてください。

発生している問題・エラーメッセージ

以下がhttps://{アプリ名}/bot/callbackに表示されます。

ValueError at /bot/callback
No JSON object could be decoded
Request Method:	GET
Request URL:	https://dry-dusk-55498.herokuapp.com/bot/callback
Django Version:	1.10.3
Exception Type:	ValueError
Exception Value:	
No JSON object could be decoded
Exception Location:	/app/.heroku/python/lib/python2.7/json/decoder.py in raw_decode, line 382
Python Executable:	/app/.heroku/python/bin/python
Python Version:	2.7.15
Python Path:	
['/app/.heroku/python/bin',
 '/app',
 '/app/.heroku/python/lib/python27.zip',
 '/app/.heroku/python/lib/python2.7',
 '/app/.heroku/python/lib/python2.7/plat-linux2',
 '/app/.heroku/python/lib/python2.7/lib-tk',
 '/app/.heroku/python/lib/python2.7/lib-old',
 '/app/.heroku/python/lib/python2.7/lib-dynload',
 '/app/.heroku/python/lib/python2.7/site-packages']
Server time:	Thu, 7 Jun 2018 17:50:49 +0000

該当のソースコード

python
1from django.shortcuts import render
2from django.http import HttpResponse
3import json
4import requests
5import re
6import urllib
7
8REPLY_ENDPOINT = 'https://api.line.me/v2/bot/message/reply'
9ACCESS_TOKEN = "AjVgISkuYRmpS+DKpT6pqs7wp6Lzb0qT482VpiWjXTDEUK06KWSjk477LwVO6qp/z1fNdwmuxyCj3yBvipfWMFVptvBdcT0Annc0M9F2ym5wsoDdsfMQPclamBgbIu7BkJHhTuAoqDGuayZiEHdx1AdB04t89/1O/w1cDnyilFU="
10HEADER = {
11    "Content-Type": "application/json",
12    "Authorization": "Bearer " + ACCESS_TOKEN
13}
14
15def index(request):
16    return HttpResponse("This is bot api.")
17
18def callback(request):
19    reply = ""
20    request_json = json.loads(request.body.decode('utf-8'))
21    for e in request_json['events']:
22        reply_token = e['replyToken']
23        message_type = e['message']['type']
24
25        if message_type == 'text':
26            text = e['message']['text']
27            reply += reply_text(reply_token, text)
28    return HttpResponse(reply)
29
30def reply_text(reply_token, text):
31    reply = word_search(text)
32    payload = {
33          "replyToken":reply_token,
34          "messages":[
35                {
36                    "type":"text",
37                    "text": reply
38                }
39            ]
40    }
41
42    requests.post(REPLY_ENDPOINT, headers=HEADER, data=json.dumps(payload))
43    return reply
44
45def word_search(text):
46    err = False
47    x = text
48    url = 'https://ejje.weblio.jp/content/' + x.replace(' ','+')
49    response = urllib.request.urlopen(url).read().decode('utf-8')
50
51    repro = re.search(r'<span class=phoneticEjjeDesc>(.*?)<',response)
52    if repro != None:
53      pro = repro.group(1)
54    else:
55      pro = ''
56
57    remean = re.search(r'<meta name="twitter:description" content="(.*?)"',response)
58    if remean == None:
59      err = True
60    mean = remean.group(1)
61
62    url = 'https://dictionary.cambridge.org/dictionary/learner-english/' + x.replace(' ','-')
63    response = urllib.request.urlopen(url).read().decode('utf-8')
64    reenmean = re.search(r'<meta name="description" content="(.*?)Learn more."',response)
65    if reenmean == None:
66      err = True
67    enmean = reenmean.group(1)
68
69    return "{}\n{}\n{}\n{}".format(x, pro, mean, enmean)