Fix test_shutils when there is “python3” but no “python”

[musicinmybrain]

This allows the tests to pass in environments where the Python interpreter has some other name, such as “python3”.

This allows the tests to pass in environments where there is a “python3” but no “python” in the executable search path.

[mmckerns]

Can you clarify what your intended changes are doing, or what errors you may be seeing to trigger your changes?

The intent of which('python') is not to find the current interpreter being used. It's to find the path to the first (or all) executables named "python" in the user's PATH. So, if I was running python 3.10, and had several instances of python installed (including multiple instances of 3.10), I might expect results like these:

>>> from pox import *
>>> which('python')
'/usr/bin/python'
>>> which('python3')
'/opt/local/Library/Frameworks/Python.framework/Versions/3.10/bin/python3'
>>> which('python3.10')
'/opt/local/bin/python3.10'
>>>
>>> which_python()
'/opt/local/bin/python3.10'

The last case, using which_python is intended to find the version/path for the current executable.

[musicinmybrain]

When building RPMs for Fedora Linux, there is no executable called python in the PATH in the build environment—only python3. (Installed systems typically, but not necessarily, have /usr/bin/python provided by the python-unversioned-command RPM.) This means the tests fail when building a python-pox RPM.

My idea was that, if the test suite is invoked with something like /usr/bin/python3, then searching for python3 will work even if there is no /usr/bin/python.

If you don’t think this makes sense, we can always keep skipping the test in the RPM build, or carry a simpler downstream-only patch that simply replaces each 'python' string in this test with 'python3'.

[mmckerns]

Ah... ok. I see, that's a case I didn't plan for. How about something like this:

python = 'python' if which('python') else 'python3'
assert which(python).endswith((python,'python.exe'))
assert which(python) in which(python,all=True)

You can update the PR if that works for you.

[musicinmybrain]

Thanks for the suggestion. I will update the PR.

[musicinmybrain]

Thanks!

[mmckerns]

thank you for the PR