it doesn't work cuz Python version is not suitable

[Shoichiro Takahashi]

Error log is below

-----> Python app detected
 !     The latest version of Python 3 is python-3.6.2 (you are using python-3.5.1, which is unsupported).
 !     We recommend upgrading by specifying the latest version (python-3.6.2).
       Learn More: https://devcenter.heroku.com/articles/python-runtimes
-----> Installing python-3.5.1
 !     Requested runtime (python-3.5.1) is not available for this stack (heroku-16).
 !     Aborting.  More info: https://devcenter.heroku.com/articles/python-support
 !     Push rejected, failed to compile Python app.
 !     Push failed

So runtime.txt change to "python-3.6.2"

[Lucas Mezêncio]

@Lexion13 just update your runtime.txt to python=3.6.3. 😉

[Amritpal singh]

Heroku support only few python versions - latest one being python-3.8.3 as of today.

Check this https://devcenter.heroku.com/articles/python-support#supported-runtimes