How to overcome 'Coudn't find that formation' error when adding web dynos to Heroku django app?

To state the obvious: another way to encounter this issue is if you're working on a new app, and you try running heroku ps:scale web=1 before you've actually done a git push heroku master. There is no Procfile on the Heroku server in that case, because there aren't any files at all. :D

Ensure that your Procfile has no extension.

To create a file with no extension on Windows, you can use the command notepad Procfile. from the command line.

To add yet another reason this can happen, my Procfile contained

web:gunicorn 

but it should be:

web: gunicorn

As far as I can tell from all of these answers, if you run into this problem, it is very likely related to Procfile.