Google Calendar API for OAuth Web Application in Python Flask

I have been all over SO and SE looking for the particular answer to this question and cannot seem to find the answer. I am building a simple web application that uses Python Flask to access Google Calendar and fill out the calendar based on conditions. My issue is with OAuth2 and getting the redirect_uris correct. Below is my code, and every time I try to run my code I get an error that the redirect URI is incorrect and the app will not go any further. The redirect uri it seems to be obsessed with is http://localhost:8080. I have tried setting adding that redirect URI to my developers console, adding that URI with a tailing '/oauth2callback' (with and without a tailing '/'). I have also tried specifying a different URI entirely, but the error keeps mentioning http://localhost:8080 and never seems to recognize any other redirect URI despite using different client_secret.json files and specifying other uri's in flow_from_client_secrets. I have also cleared my cache before running the script every time as well as running things in chrome's incognito mode. Nothing seems to help. I know it must be something simple, and if somebody could point out what it was, I would be very appreciative!

SCOPES = 'https://www.googleapis.com/auth/calendar'
CLIENT_SECRET_FILE = 'client_secret_web.json'
APPLICATION_NAME = 'Example Calendar Application'
REDIRECT_URI = 'http://placeholder.com/oauth2callback'

home_dir = os.path.expanduser('~')
    credential_dir = os.path.join(home_dir, '.credentials')
    if not os.path.exists(credential_dir):
        os.makedirs(credential_dir)
    redirect_uri=""
    credential_path = os.path.join(credential_dir,
                                   'calendar-python-quickstart.json')

    store = Storage(credential_path)
    credentials = store.get()
    flow = client.flow_from_clientsecrets(self.CLIENT_SECRET_FILE, 
    self.SCOPES, prompt='consent', redirect_uri=self.REDIRECT_URI)
    flow.user_agent = self.APPLICATION_NAME
    if self.flags:
        credentials = tools.run_flow(flow, store, self.flags)
    else: # Needed only for compatibility with Python 2.6
        credentials = tools.run(flow, store)

        print('Storing credentials to ' + credential_path)
    return credentials