otree zip command creates a runtime.txt with the line "python-3.9.13"

This is not a valid python version according to the Heroku documentation.

I am getting the following error message when deploying through the oTree Hub:

********************************************************
python-3.9.13

Build output
-----> Building on the Heroku-22 stack
-----> Determining which buildpack to use for this app
-----> Python app detected
-----> Using Python version specified in runtime.txt
 !     
 !     A Python security update is available! Upgrade as soon as possible to: python-3.9.16
 !     See: https://devcenter.heroku.com/articles/python-runtimes
 !     
-----> Installing python-3.9.13
-----> Installing pip 23.0.1, setuptools 63.4.3 and wheel 0.38.4
-----> Installing SQLite3
-----> Installing requirements with pip
       ERROR: Could not find a version that satisfies the requirement settings.py (from versions: none)
       ERROR: No matching distribution found for settings.py
 !     Push rejected, failed to compile Python app.

 !     Push failed
 
 **********************************
 
 Any ideas?

The error is not about the python version; it's that you seem to have a line 'settings.py' in your requirements.txt. Delete that line.

Thank you Chris.  This resolved the problem described above.