Django: Heroku Failing to launch, at=error code=H10 desc="App crashed"

It looks like heroku can't start the webserver and so changed the app status to crashed. Everytime when I get this error code the Procfile was misconfigured or had errors.

The same error occurs when the gunicorn package is not installed (in your virtualenv). Here is a similar traceback as of October 2016:

2016-10-21T08:35:56.041002+00:00 heroku[router]: at=error code=H10 
desc="App crashed" method=GET path="/" host=mygreatapp.herokuapp.com 
request_id=blablabla fwd="188.73.193.22" dyno= connect= service= 
status=503 bytes=

I was so impatient and during the conversion of my local app to a Heroku one (which includes the creation of Procfile, runtime.txt, .gitignore files, installation of dj-database-url, whitenoise) I forgot to install the most important package (pip install gunicorn)!!!

Doing so, H10 error vanished!

cheers!