Update supported python versions

[altheaden]

Support for Python 3.8 (and lower) has been dropped from conda-forge, so I've updated the lower bounds of supported versions here accordingly.

---

Updated template from @forsyth2:

Issue resolution

• Equivalent to Drop support for python 3.8 e3sm_diags#844, Update supported python versions zppy#620

This pull request is a minor adjustment that would increment the patch version.

1. Does this do what we want it to do?

Objectives:

• Make Python 3.9 the oldest supported Python version in zstash.

Required:

• Product Management: I have confirmed with the stakeholders that the objectives above are correct and complete.
• Testing: I have added at least one automated test. Every objective above is represented in at least one test.
  • Existing unit tests are sufficient to cover this change.
• Testing: I have considered likely and/or severe edge cases and have included them in testing.

2. Are the implementation details accurate & efficient?

Required:

• Logic: I have visually inspected the entire pull request myself.

3. Is this well documented?

Required:

• Documentation: by looking at the docs, a new user could easily understand the functionality introduced by this pull request.
• This change does not require new documentation.

4. Is this code clean?

Required:

• Readability: The code is as simple as possible and well-commented, such that a new team member could understand what's happening.
• Pre-commit checks: All the pre-commits checks have passed.

[xylar]

@forsyth2, same as on zppy, could you let CI run here and on #352, and can you suggest what tests (other than CI) you'd like to see?

[forsyth2]

I have inspected the code visually and have run the unit tests*. I will merge this change. Thanks @altheaden.

*If interested, my workflow for running the tests was:

source /global/homes/f/forsyth/miniconda3/etc/profile.d/conda.sh
conda env list
git remote add altheaden git@github.com:altheaden/zstash.git
git fetch altheaden update-python-versions
git checkout -b test-351 altheaden/update-python-versions
mamba clean --all
mamba env create -f conda/dev.yml -n zstash_test_351
conda activate zstash_test_351
pip install .

# Follow directions from https://github.com/E3SM-Project/zstash/discussions/329
rm ~/.globus-native-apps.cfg
# On Globus, activate NERSC Perlmutter, NERSC HPSS endpoints
cd ../zstash_runs/
mkdir zstash_demo; echo 'file0 stuff' > zstash_demo/file0.txt
zstash create --hpss=globus://6c54cade-bde5-45c1-bdea-f4bd71dba2cc/~/manual_run zstash_demo
# Enter auth code twice
cd -

# Run unit tests
python -m unittest tests/test_*.py
# All tests pass