from flask import Flask

app = Flask(__name__)

@app.route('/')
def hello():
    return 'Hello world'

if __name__ == '__main__':
    app.run()

web: gunicorn server:app --log-file=-

Flask==0.10.1
Jinja2==2.8
MarkupSafe==0.23
Werkzeug==0.10.4
itsdangerous==0.24

heroku login
heroku create
source venv/bin/activate
pip3 install Flask gunicorn

runtime: failed to create new OS thread (have 6 already; errno=11)
fatal error: newosproc