I am trying to retrieve events from a public group calendar to display on a Flask based website in custom HTML style via the Google Calendar API.
I have followed the documentation's quickstart guide on how to use Python to get events from the API. I have successfully managed to do this and the results are displayed in the console.
Now, I am trying to get this to work in my Flask app, however, I am unable to proceed with the formatting of the results, as I cannot even authenticate access to the API. I am not sure whether I am doing something completely stupid or silly, but several hours of debugging and Googling have not been able to resolve the issue.
I am given the following error regardless of whether I have already made the credentials file in the same directory using the quickstart example code. Note, I am using blueprints in Flask, using a common directory structure. The code below is of part of one of my blueprints that has the client_secret file and credentials file in the same directory as the main python file of that blueprint.
...    
FileNotFoundError: [Errno 2] No such file or directory: 'client_secret.json'
...
oauth2client.clientsecrets.InvalidClientSecretsError: ('Error opening file', 'client_secret.json', 'No such file or directory', 2)
Code:
@event_site.route('/events')
def events():
    # Setup the Calendar API
    SCOPES = 'https://www.googleapis.com/auth/calendar.readonly'
    store = file.Storage('credentials.json')
    creds = store.get()
    if not creds or creds.invalid:
        flow = client.flow_from_clientsecrets('client_secret.json', SCOPES)
        creds = tools.run_flow(flow, store)
    service = build('calendar', 'v3', http=creds.authorize(Http()))
    # Call the Calendar API
    now = datetime.datetime.utcnow().isoformat() + 'Z'  # 'Z' indicates UTC time
    print('Getting the upcoming 10 events')
    events_result = service.events().list(calendarId='id@group.calendar.google.com',
                                          timeMin=now,
                                          maxResults=10, singleEvents=True,
                                          orderBy='startTime').execute()
    events = events_result.get('items', [])
    if not events:
        print('No upcoming events found.')
    for event in events:
        start = event['start'].get('dateTime', event['start'].get('date'))
        print(start, event['summary'])
    return render_template('cadet_events.html')
Thanks in advance.
