OAuth2 Authorize Route for Google Calendar API

auth.py

import flask
import google.oauth2.credentials
import google_auth_oauthlib.flow
import os
from flask import Flask
from flask import redirect
from flask import request
from googleapiclient.discovery import build

# set up a Flow object that reads the clients from our secrets file with the 
# corresponding scope 
flow = google_auth_oauthlib.flow.Flow.from_client_secrets_file(
    'client_secrets.json',
    scopes=['https://www.googleapis.com/auth/calendar'])

# indicate the redirect URI that we placed in the console redirect URI when we 
# created the oauth credentials 
flow.redirect_uri = 'http://localhost:8080/oauth2redirect'

# generates the auth URL that we need to redirect users to where the user 
# gets the oauth consent screen and we get the access code to later exchange for an
# auth token
authorization_url, _ = flow.authorization_url(
    # enables us to grab a refresh token without the user granting us access 
    # a second time if needed
    access_type='offline',
    include_granted_scopes='true')

# create our Flask web app
app = Flask(__name__)

# this allows transport over HTTP for development purposes, if excluded
# HTTPS is needed
os.environ['OAUTHLIB_INSECURE_TRANSPORT'] = '1'

@app.route("/authorize-user")
def auth_user():
    """
    Redirects a user to Google's authorization server to show the OAuth
    Consent screen and get user consent.
    """
    return redirect(authorization_url)