Running this app results in this error:
<[OVER QUERY LIMIT] Google - Geocode [empty]>

The error occurs in models.py at this point:

def address_to_latlng(self, address):
    g = geocoder.google(address)

A key is required for the query to work.

{
   "error_message" : "Keyless access to Google Maps Platform is deprecated. Please use an API key with all your API calls to avoid service interruption. For further details please refer to http://g.co/dev/maps-no-account",
   "results" : [],
   "status" : "OVER_QUERY_LIMIT"
}

Edit: The Google Geocode API requires a signup with billing details for an API key from June 2018. I switched to the Bing Maps API by signing up here (https://www.bingmapsportal.com/), and generating a key. It doesn't require any billing details.

1. Replace geocode.google() with geocode.bing() in models.py.
2. Save the key to env with heroku config key_bingmaps=[INSERT KEY HERE] in the terminal.
3. Import key as variable import os geocode.bing(address, key=os.environ.key_bingmaps in models.py.