Add Python 3.9 support

[hugovk]

Python 3.9.0 was released today, 2020-10-05:

• https://discuss.python.org/t/python-3-9-0-is-now-available-and-you-can-already-test-3-10-0a1/5375?u=hugovk

Please could you also add support in GitHub Actions for Python 3.9?

Thank you!

PS It took 21 days for 3.8: #30 (comment)

[maxim-lobanov]

Hello everyone:
Python 3.9 is already available (It is not pre-cached on image yet, so it will be installed on-flight with minor latency):

- uses: actions/setup-python@v2
  with:
    python-version: '3.9'

We also going to deploy new image with pre-cached Python 3.9 next week.

[hugovk]

Confirmed it's now available on GHA, thank you!

Took ~10s to install on Linux, ~60s on macOS and ~51s on Windows, not a problem for me, and good to hear the pre-cached images is coming soon.

https://github.com/hugovk/test/runs/1215290584?check_suite_focus=true

Run actions/setup-python@v2
Version 3.9 was not found in the local cache
Version 3.9 is available for downloading
Download from "actions/python-versions@3.9.0-83838 python-3.9.0-linux-20.04-x64.tar.gz (download)"
Extract downloaded archive
/usr/bin/tar xz --warning=no-unknown-keyword -C /home/runner/work/_temp/e8e512d5-ecbb-4563-9374-a1796267419e -f /home/runner/work/_temp/e9bdf138-7f69-49ec-8166-59a47b1d3ef4
Execute installation script
Check if Python hostedtoolcache folder exist...
Create Python 3.9.0 folder
Copy Python binaries to hostedtoolcache folder
Create additional symlinks (Required for the UsePythonVersion Azure Pipelines task and the setup-python GitHub Action)
Upgrading PIP...
Looking in links: /tmp/tmpiitvwvjj
Requirement already satisfied: setuptools in /opt/hostedtoolcache/Python/3.9.0/x64/lib/python3.9/site-packages (49.2.1)
Requirement already satisfied: pip in /opt/hostedtoolcache/Python/3.9.0/x64/lib/python3.9/site-packages (20.2.3)
Collecting pip
Downloading pip-20.2.3-py2.py3-none-any.whl (1.5 MB)
Installing collected packages: pip
Successfully installed pip-20.2.3
Create complete file
Successfully setup CPython (3.9.0)

[hugovk]

PS It took 21 days for 3.8: #30 (comment)

This time: 18 hours! 🎈