Python 3.9.20 Upgrade

[Kevin Thomas]

Hi Oppia Devs,

We have recently merged a PR that upgrades the Python version to 3.9.20 (See #21215 -- thanks Sean!)

Please follow these instructions on your local Oppia setup:

1. Delete third_party/python_libs and third_party/python3_libs so that these can be cleanly reinstalled.

2. Developers who are using the Python installation should also upgrade pyenv, as follows:

• Run "cd ~/.pyenv/plugins/python-build/../.. && git pull && cd -"
• Run "pyenv install 3.9.20"
• Update the version in the .pyenv file in oppia/ to 3.9.20

3. Test the installation by running python -m scripts.start.

Thanks,
Kevin