deploying python flask app on heroku gives error with functools32

Question

First question on stackoverflow :D (because I found almost everything until now).

I try to deploy my python app to Heroku, but the following error appears:

git push heroku master
Counting objects: 7036, done.
Compressing objects: 100% (3933/3933), done.
Writing objects: 100% (7036/7036), 10.97 MiB | 338.00 KiB/s, done.
Total 7036 (delta 2020), reused 7021 (delta 2014)
remote: Compressing source files... done.
remote: Building source:
remote: 
remote: -----> Python app detected
remote: -----> Installing python-3.6.2
remote: -----> Installing pip
remote: -----> Installing requirements with pip
remote:        Collecting aniso8601==1.2.1 (from -r /tmp/build_3d7108e037a9a8803be5100bdc092768/requirements.txt (line 1))
remote:          Downloading aniso8601-1.2.1.tar.gz (62kB)
remote:        Collecting click==6.7 (from -r /tmp/build_3d7108e037a9a8803be5100bdc092768/requirements.txt (line 2))
remote:          Downloading click-6.7-py2.py3-none-any.whl (71kB)
remote:        Collecting cycler==0.10.0 (from -r /tmp/build_3d7108e037a9a8803be5100bdc092768/requirements.txt (line 3))
remote:          Downloading cycler-0.10.0-py2.py3-none-any.whl
remote:        Collecting deap==1.0.2.post2 (from -r 
remote:        Collecting Flask==0.12.2 (from -r /tmp/build_3d7108e037a9a8803be5100bdc092768/requirements.txt (line 5))
remote:          Downloading Flask-0.12.2-py2.py3-none-any.whl (83kB)
remote:        Collecting Flask-RESTful==0.3.6 (from -r /tmp/build_3d7108e037a9a8803be5100bdc092768/requirements.txt (line 6))
remote:          Downloading Flask_RESTful-0.3.6-py2.py3-none-any.whl
remote:        Collecting functools32==3.2.3.post2 (from -r /tmp/build_3d7108e037a9a8803be5100bdc092768/requirements.txt (line 7))
remote:          Downloading functools32-3.2.3-2.zip
remote:            Complete output from command python setup.py egg_info:
remote:            This backport is for Python 2.7 only.
remote:            
remote:            ----------------------------------------
remote:        Command "python setup.py egg_info" failed with error code 1 in /tmp/pip-build-l0v0636d/functools32/
remote:  !     Push rejected, failed to compile Python app.
remote: 
remote:  !     Push failed
remote: Verifying deploy...
remote: 
remote: !   Push rejected to XXXXXXX (servername by Heroku).
remote: 

On my virtual box everything works fine if I do

pip install -r requirements.txt

I tried the following with no avail:

• changing functools32 version
• Removing functools from requirements text, which made me realize it is a dependency by Flask for decorators :(

Answer 1

Answer (thanks to the comments): I didn't realize that I used python 2.7 (again, I am a beginner) in my virtualenv. Seems that using then the functools somewhere automatically installed the functools32 package which ports the functools from python 3 to 2. Heroku is using python 3 by default, so that is why functools32 is probably not available.

I now installed a python 3 virtual environment thanks to this post, ported the few things I hat to port from 2 to 3 and everything works like a charm.

Thanks to davidism & dimmg to point me into the right direction.