LINEBOTをPythonで作りたいのですが、アプリのページが開けません

前提・実現したいこと

pythonを使ってそれをherokuにデプロイしてlineのおうむ返しのプログラムを作ろうとしています。

以下のサイトを参考にしました。

https://qiita.com/krocks96/items/67f7510b36945eb9689b

発生している問題・エラーメッセージ

そのサイトのうURLを開くと、

Not Found

The requested URL was not found on the server. If you entered the URL manually please check your spelling and try again.

と出て来ます。

また、linedeveloperのwebhookの設定のところでは「Webhookが無効なHTTPステータスコードを返しました（期待されるステータスコードは200です）」

そこでherokuのlogを確認したところ、以下のようなlogがでました。(一部省略）

ユーザ名395+00:00 app[web.1]: reraise(exc_type, exc_value, tb)
2018-10-30T08:47:34.703396+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/flask/_compat.py", line 33, in rer
aise
2018-10-30T08:47:34.703399+00:00 app[web.1]: raise value
2018-10-30T08:47:34.703400+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/flask/app.py", line 1612, in full_
dispatch_request

2018-10-30T08:47:34.703402+00:00 app[web.1]: rv = self.dispatch_request()
2018-10-30T08:47:34.703403+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/flask/app.py", line 1598, in dispa
tch_request
2018-10-30T08:47:34.703406+00:00 app[web.1]: return self.view_functions[rule.endpoint](**req.view_args)
2018-10-30T08:47:34.703407+00:00 app[web.1]: File "line_bot.py", line 37, in callback
2018-10-30T08:47:34.703409+00:00 app[web.1]: handler.handle(body, signature)
2018-10-30T08:47:34.703411+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/linebot/webhook.py", line 227, in
handle
2018-10-30T08:47:34.703412+00:00 app[web.1]: func(event)
2018-10-30T08:47:34.703414+00:00 app[web.1]: File "line_bot.py", line 48, in handle_message
2018-10-30T08:47:34.703415+00:00 app[web.1]: TextSendMessage(text=event.message.text))
2018-10-30T08:47:34.703417+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/linebot/api.py", line 94, in reply
_message
2018-10-30T08:47:34.703418+00:00 app[web.1]: '/v2/bot/message/reply', data=json.dumps(data), timeout=timeout
2018-10-30T08:47:34.703420+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/linebot/api.py", line 372, in _pos
t
2018-10-30T08:47:34.703422+00:00 app[web.1]: self.__check_error(response)
2018-10-30T08:47:34.703423+00:00 app[web.1]: File "/app/.heroku/python/lib/python3.6/site-packages/linebot/api.py", line 381, in __ch
eck_error
2018-10-30T08:47:34.703425+00:00 app[web.1]: raise LineBotApiError(response.status_code, error)
2018-10-30T08:47:34.706887+00:00 app[web.1]: linebot.exceptions.LineBotApiError: <LineBotApiError [Invalid reply token]>
2018-10-30T08:47:34.710948+00:00 app[web.1]: 10.111.224.2 - - [30/Oct/2018 08:47:34] "POST /callback HTTP/1.1" 500 -
2018-10-30T08:49:24.578305+00:00 heroku[router]: at=info method=GET path="/" host=linebot-0328.herokuapp.com request_id=beda40f7-1ba4
-4ada-a8ef-dbb9c0307d6b fwd="103.5.140.176" dyno=web.1 connect=1ms service=4ms status=404 bytes=380 protocol=https
2018-10-30T08:49:24.578038+00:00 app[web.1]: 10.31.74.203 - - [30/Oct/2018 08:49:24] "GET / HTTP/1.1" 404 -
2018-10-30T08:49:25.650288+00:00 heroku[router]: at=info method=GET path="/" host=linebot-0328.herokuapp.com request_id=3dbf0cf7-f72c
-4018-87f6-81466771dd7b fwd="103.5.140.176" dyno=web.1 connect=2ms service=7ms status=404 bytes=380 protocol=https
2018-10-30T08:49:25.649929+00:00 app[web.1]: 10.31.74.203 - - [30/Oct/2018 08:49:25] "GET / HTTP/1.1" 404 -
2018-10-30T08:49:26.546435+00:00 heroku[router]: at=info method=GET path="/" host=linebot-0328.herokuapp.com request_id=dc91cbb5-891d
-4c3d-b243-53232b0b5ba2 fwd="103.5.140.176" dyno=web.1 connect=1ms service=5ms status=404 bytes=380 protocol=https
2018-10-30T08:49:26.546093+00:00 app[web.1]: 10.31.74.203 - - [30/Oct/2018 08:49:26] "GET / HTTP/1.1" 404 -
2018-10-30T08:49:26.885646+00:00 heroku[router]: at=info method=GET path="/" host=linebot-0328.herokuapp.com request_id=b7ba7d39-16c9
-4dc3-939d-4051bf221e07 fwd="103.5.140.176" dyno=web.1 connect=1ms service=3ms status=404 bytes=380 protocol=https

2018-10-30T08:49:26.885377+00:00 app[web.1]: 10.31.74.203 - - [30/Oct/2018 08:49:26] "GET / HTTP/1.1" 404 -
2018-10-30T08:51:57.508440+00:00 heroku[router]: at=info method=GET path="/" host=linebot-0328.herokuapp.com request_id=5bd7f782-d6b7
-4322-8454-ffd03fc13e5b fwd="103.5.140.176" dyno=web.1 connect=0ms service=10ms status=404 bytes=380 protocol=https
2018-10-30T08:51:57.503725+00:00 app[web.1]: 10.45.249.93 - - [30/Oct/2018 08:51:57] "GET / HTTP/1.1" 404 -
2018-10-30T09:20:35.000000+00:00 app[api]: Build started by user ユーザ名
2018-10-30T09:20:51.139009+00:00 heroku[web.1]: Restarting
2018-10-30T09:20:51.139788+00:00 heroku[web.1]: State changed from up to starting
2018-10-30T09:20:52.184553+00:00 heroku[web.1]: Stopping all processes with SIGTERM
2018-10-30T09:20:52.340375+00:00 heroku[web.1]: Process exited with status 143
2018-10-30T09:20:50.835138+00:00 app[api]: Release v7 created by user ユーザ名
2018-10-30T09:20:50.835138+00:00 app[api]: Deploy 04973591 by user ユーザ名
2018-10-30T09:20:55.703663+00:00 heroku[web.1]: Starting process with command `python line_bot.py`
2018-10-30T09:21:01.131131+00:00 heroku[web.1]: State changed from starting to up
2018-10-30T09:21:00.954198+00:00 app[web.1]: * Running on http://0.0.0.0:41461/ (Press CTRL+C to quit)
2018-10-30T09:20:59.000000+00:00 app[api]: Build succeeded
2018-10-30T09:21:35.673786+00:00 heroku[router]: at=info method=GET path="/" host=linebot-0328.herokuapp.com request_id=bec43206-658d
-4b02-a79b-e51e11cd2571 fwd="103.5.140.176" dyno=web.1 connect=1ms service=55ms status=404 bytes=380 protocol=https
2018-10-30T09:21:35.669787+00:00 app[web.1]: 10.11.176.130 - - [30/Oct/2018 09:21:35] "GET / HTTP/1.1" 404 -
2018-10-30T09:22:36.274038+00:00 heroku[router]: at=info method=GET path="/" host=linebot-0328.herokuapp.com request_id=c83500d9-3062
-4576-a3f8-a6a47107172b fwd="103.5.140.176" dyno=web.1 connect=2ms service=8ms status=404 bytes=380 protocol=https
2018-10-30T09:22:36.273479+00:00 app[web.1]: 10.45.123.32 - - [30/Oct/2018 09:22:36] "GET / HTTP/1.1" 404 -
2018-10-30T09:30:59.892002+00:00 heroku[web.1]: State changed from up to down
2018-10-30T09:31:01.092596+00:00 heroku[web.1]: Stopping all processes with SIGTERM
2018-10-30T09:31:01.196555+00:00 heroku[web.1]: Process exited with status 143
2018-10-30T09:30:59.810741+00:00 app[api]: Scaled to web@0:Free by user ユーザ名
2018-10-30T09:31:41.090859+00:00 heroku[web.1]: Starting process with command `python line_bot.py`
line_bot.py44:48
LFUTF-8Python0 files
2018-10-30T09:31:36.374119+00:00 app[api]: Scaled to web@1:Free by user ユーザ名
2018-10-30T09:31:47.103644+00:00 heroku[web.1]: State changed from starting to up
2018-10-30T09:31:46.949519+00:00 app[web.1]: * Running on http://0.0.0.0:50128/ (Press CTRL+C to quit)
2018-10-30T09:34:50.717421+00:00 app[web.1]: 10.31.74.203 - - [30/Oct/2018 09:34:50] "GET / HTTP/1.1" 404 -
2018-10-30T09:34:50.718898+00:00 heroku[router]: at=info method=GET path="/" host=linebot-0328.herokuapp.com request_id=8510f199-f5a8
-4079-be1b-0f443d5aa2a9 fwd="103.5.140.176" dyno=web.1 connect=0ms service=40ms status=404 bytes=380 protocol=https
2018-10-30T10:09:44.999647+00:00 heroku[web.1]: Idling
2018-10-30T10:09:45.000127+00:00 heroku[web.1]: State changed from up to down
2018-10-30T10:09:46.063904+00:00 heroku[web.1]: Stopping all processes with SIGTERM
2018-10-30T10:09:46.155047+00:00 heroku[web.1]: Process exited with status 143
2018-10-30T11:52:23.975527+00:00 heroku[web.1]: Unidling
2018-10-30T11:52:23.976430+00:00 heroku[web.1]: State changed from down to starting

該当のソースコード

pythonのソースコードです

from linebot import (
    LineBotApi, WebhookHandler
)

from flask import Flask, request, abort

from linebot.exceptions import (
    InvalidSignatureError
)
from linebot.models import (
    MessageEvent, TextMessage, TextSendMessage,
)
import os

app = Flask(__name__)

#YOUR_CHANNEL_ACCESS_TOKEN = os.environ["YOUR_CHANNEL_ACCESS_TOKEN"]
#YOUR_CHANNEL_SECRET = os.environ["YOUR_CHANNEL_SECRET"]

YOUR_CHANNEL_ACCESS_TOKEN = "アクセストークン"
YOUR_CHANNEL_SECRET = "チャンネルシークレット"

line_bot_api = LineBotApi(YOUR_CHANNEL_ACCESS_TOKEN)
handler = WebhookHandler(YOUR_CHANNEL_SECRET)

@app.route("/callback", methods=['POST'])
def callback():
    # get X-Line-Signature header value
    signature = request.headers['X-Line-Signature']

    # get request body as text
    body = request.get_data(as_text=True)
    app.logger.info("Request body: " + body)

    # handle webhook body
    try:
        handler.handle(body, signature)
    except InvalidSignatureError:
        abort(400)

    return 'OK'


@handler.add(MessageEvent, message=TextMessage)
def handle_message(event):
    line_bot_api.reply_message(
        event.reply_token,
        TextSendMessage(text=event.message.text))


if __name__ == "__main__":
#    app.run()
    port = int(os.getenv("PORT", 5000))
    app.run(host="0.0.0.0", port=port)