high-level: Explicitly use python3

[wcohen]

Python3 has been released for over 15 years. Fedora, Debian, and other distributions state that python scripts should avoid using unversioned python intepreter:

https://fedoraproject.org/wiki/FinalizingFedoraSwitchtoPython3 https://www.debian.org/doc/packaging-manuals/python-policy/

The RPM build process will flag unversioned python interpreter use as an error and the build will fail. Making the papi_hl_output_writer.py explicitly use /usr/bin/python3.

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[Treece-Burgess]

@wcohen I think updating the shebang does make sense. What is your reasoning behind using #!/usr/bin/python3 instead of #!/usr/bin/env python3?

#!/usr/bin/env python3 has the pros of looking through the PATH for the Python directory, which makes the script overall more portable. Virtual environments have became increasingly more popular with even Oak Ridge pushing users to create a virtual environment if they have specific Python packages they want to use. With #!/usr/bin/python3 it assumes the Python interpreter is located there on each machine.

[wcohen]

I am open to #!/usr/bin/env python3. The original patch was a minimal change to ensure that things build on Fedora without patching. Fedora (https://fedoraproject.org/wiki/FinalizingFedoraSwitchtoPython3) mentions #!/usr/bin/env name and is okay with it. However, Debian (https://www.debian.org/doc/packaging-manuals/python-policy/) cautions against it in section 3.5.2:

Maintainers should not override the Debian Python interpreter using /usr/bin/env name. This is not advisable as it bypasses Debian’s dependency checking and makes the package vulnerable to incomplete local installations of Python.

[wcohen]

I have a branch with the #!/usr/bin/env python3. I could update the pull request with that patch if it is preferred.