Create the following .env:
FLUX_CLIENT_ID=client_id_here
FLUX_CLIENT_SECRET=client_secret_here
FLUX_REDIRECT_URI=http://localhost:5000/oauthcb
PORT=5000
SESSION_SECRET=session_secret_here
Replace client_id_here and client_secret_here with your Flux client ID/secret.
Replace session_secret_here with some arbitrary random string.
$ npm install
$ heroku local