Python buildpack, failing with undescriptive error

[lukaspj]

Hello!

I receive the following error when pushing my django application:

Counting objects: 130, done.
Delta compression using up to 4 threads.
Compressing objects: 100% (125/125), done.
Writing objects: 100% (130/130), 38.91 KiB | 0 bytes/s, done.
Total 130 (delta 41), reused 0 (delta 0)
remote: -----> Building django-test-1...
remote: -----> Python app detected
remote: -----> Installing python-3.6
remote: -----> Installing pip
remote: -----> Installing requirements with pip
remote:        /builder/buildpacks/000006_heroku-buildpack-python/bin/steps/pip-install: line 7: /app/.heroku/python/bin/pip: No such file or directory
remote: ERROR: Build failed: exec: job exited with status 1

Now, I'm certain that I'm doing something wrong. However, the error message is not very descriptive, how can I figure out what "No such file or directory" refers to?

For reference, my Profile is the following:
web: gunicorn mysite.wsgi:application --log-file -

And my requirements:

django ~= 1.11
gunicorn ~= 19.7.1

[lukaspj]

So, based no the docs which says the following:

Supported Runtimes
The latest python-2.7 and python-3.6 are officially supported, but any runtime between 2.4.4–3.6.1 can be used, including PyPy runtimes. See the buildpack’s GitHub page for a full list.

I interpreted it as "write python-3.6 in your runtime.txt, that is the officially supported". Maybe it should be clarified as python-3.6.x?

Anyways, this was clearly an error on my end. I'm both new to Flynn and Django, so I wasn't aware that Python 3.6 wasn't a valid version number.