Deploying Flask app to Heroku

I’m trying to develop my first “large” app with Flask on Heroku and I’m attempting to combine the basic tutorial here: https://devcenter.heroku.com/articles/python with the instructions here: http://flask.pocoo.org/docs/patterns/packages/#larger-applications. It works locally with “foreman start” but when I push to Heroku I get an error that the wrong port is in use: