fix: version check for standalone python

[huxuan]

• I have added a news fragment under changelog.d/ (if the patch affects the end users)

Summary of changes

Fix #1349

BTW, the changes also include some code refactor for related part.

Test plan

Tested by running

# command(s) to exercise these changes
pipx install --python 3.1 --fetch-missing-python pycowsay

[chrysle]

Thanks for catching this. A test should be useful.

[huxuan]

Thanks for catching this. A test should be useful.

Thanks for the review. A test cases for the issue is added, PTAL

Actually, I am not sure whether we should add such kind of tests since it is more like a hard-coding.

I also thought to add some positive test cases but found it will make everything a little complicated to ensure the specific python version is not available especially considering tests against all python versions and all platforms. If necessary, I might suggest to do it in a separate pull request.

[chrysle]

Actually, I am not sure whether we should add such kind of tests since it is more like a hard-coding.

I generally agree that adding tests that ensure certain features work as expected is a better way of coverage. However, this test case ensures an error is raised correctly on a certain occasion, thus I consider it useful.

I also thought to add some positive test cases but found it will make everything a little complicated to ensure the specific python version is not available especially considering tests against all python versions and all platforms.

It sounds reasonable to me to cover that.

[huxuan]

I also thought to add some positive test cases but found it will make everything a little complicated to ensure the specific python version is not available especially considering tests against all python versions and all platforms.

It sounds reasonable to me to cover that.

OK, I just forgot the usage of monkey mock and learned from other places, will add some more cases later.

[chrysle]

Thanks!