Failed to detect set buildpack when it's just been set for Python?

Question

I've been trying to push a django web app to heroku with no avail because of the following error:

(venv)douglaswong@Douglas-MacBook-Pro ~/testing (testing)$ git push heroku master
Counting objects: 53, done.
Delta compression using up to 4 threads.
Compressing objects: 100% (35/35), done.
Writing objects: 100% (53/53), 41.11 KiB | 0 bytes/s, done.
Total 53 (delta 12), reused 48 (delta 11)
remote: Compressing source files... done.
remote: Building source:
remote:
remote: -----> Fetching set buildpack git://github.com/heroku/heroku-buildpack-python.git... done
remote:
remote:  !     Push rejected, failed to detect set buildpack git://github.com/heroku/heroku-buildpack-python.git
remote: More info: https://devcenter.heroku.com/articles/buildpacks#detection-failure
remote:
remote: Verifying deploy...
remote:
remote: !   Push rejected to sleepy-spire-9508.
remote:
To https://git.heroku.com/sleepy-spire-9508.git
 ! [remote rejected] master -> master (pre-receive hook declined)
error: failed to push some refs to 'https://git.heroku.com/sleepy-spire-9508.git'

It says it failed to detect set buildpack. However, I had set it with

(venv)douglaswong@Douglas-MacBook-Pro ~/testing (testing)$ heroku create --buildpack git://github.com/heroku/heroku-buildpack-python.git
Creating fierce-waters-9228... done, stack is cedar-14
Buildpack set. Next release on fierce-waters-9228 will use git://github.com/heroku/heroku-buildpack-python.git.
https://fierce-waters-9228.herokuapp.com/ | https://git.heroku.com/fierce-waters-9228.git

What are some possible causes for this? I currently have these files in my root directory if it makes a difference:

Procfile         angellistJob     venv
README.md        requirements.txt

Any advice is appreciated, thank you!

Answer 1

I had a similar issue. For me the problem was that I forgot to commit the changes to my local repo.

Also, make sure you commit to the same branch you're pushing to.

Hope this helps!

Answer 2

Just to bring to the notice of anyone who has the same problem. Even I had the same problem and was committing to the exact branch I was pushing to. However, since I didn't have the requirements.txt file, the push was being rejected.
So, also make sure you have the Procfile and the requirements.txt before pushing to heroku.

Answer 3

I found out that this issue might occur for two reasons:

• There isn't the requirements.txt file in the current directory.
• You are pushing on a different branch.

On the other hand you could set the respective buildpacks at the moment of create the app.

heroku create myapp --buildpack heroku/python