which btw wouldn't help at all with op's scenario of Python 2 scripts finding an unexpected Python 3 interpreter.

Exactly. Whenever a script is made, it should have #!/usr/bin/env interpreter# as the first line.

#!/usr/bin/env python2 #!/usr/bin/env python3

Explicitly declaring the required version fixes that problem. In arch, most of the PKGBUILDs will have a line to sed the explicit line into the file in place of the generic python line.