Python on path

[mmarchetti]

This PR changes how we handle finding the active Python executable, if one isn't specified.

We previously tried to find python on PATH; this PR adds a fallback to python since some installs do not include an executable named python3.

Intent

Fixes #172

Type of Change

• Bug Fix
• New Feature
• Breaking Change

Automated Tests

There are unit tests covering this change.

Directions for Reviewers

Re-test the Windows scenario in #172 and verify that if python is on PATH but python3 is not, we use the python executable.

[sagerb]

Is it possible that you need to change the base of this PR, as it seems to include a lot more than just support for finding python or python3? Otherwise, if this is what you intended, you should update the description and get validation instructions in there for the other changes.

[kgartland-rstudio]

I suspect this isn't quite ready but I just grabbed the binary from GH Actions and it's still failing when I don't have a python3.exe. Here's a gif of what's I'm seeing when using this build:

The error when there is no python3.exe:

time=2023-10-16T13:05:47.759-04:00 level=ERROR msg="Error running command" error="exit status 9009"

PYTHONPATH=C:\Users\kgartland\AppData\Local\Programs\Python\Python311
PATH=C:\Users\kgartland\AppData\Local\Programs\Python\Python311\

[kgartland-rstudio]

Looks like the culprit is the App Execution Alias setting, when disabling for python3.exe, the publish ui works:

By default that's enabled though, so we should find the appropriate app alias regardless of whether or not there is a python3.exe file.

[kgartland-rstudio]

Verifed fix! New build works with no python3.exe with and without App Execution Alias set.