Python 3.6 is no longer supported
Change effective on 21 February 2023
Python 3.6 reached upstream end-of-life on December 23rd, 2021, and no longer receives security or bug fixes. Apps still using it contain potential security vulnerabilities. Upgrade them to a newer version of Python as soon as possible.
To raise awareness of this end-of-life, the Python buildpack has been outputting deprecation warnings in the build log for some time. As of today, the latest version of the Python buildpack rejects builds of apps using Python 3.6.
Existing Python 3.6 apps continue to run, however, you must upgrade them to a newer version of Python before you can perform any further builds/code deployments.
If you are not able to update to Python 3.6 now, you must switch from the default heroku/python buildpack to a buildpack URL of https://github.com/heroku/heroku-buildpack-python#v227 (the previous buildpack version) in order to continue building. However, this must only be used as a short-term workaround, and after upgrading to newer Python you must remember to switch back to the heroku/python stable release. For more information, see checking the Python buildpack version.