That, unfortunately, only works if you don't need to maintain backwards compatibility with older systems. `python` will exist and point to python2 on any system. `python2` may not if it predates or ignores the PEP. `python3` didn't even come installed by default on a lot of nixes until recently, making it the worst of option of the three.

Of course, it will take time for this to become effective. But this is the portable solution. Systems for which this does not work are broken and should be fixed, software should not be updated to accomodate for broken systems.

>software should not be updated to accomodate for broken systems.

Its not. The software was written, and maintains, backwards compatibility with systems that predate or partially predate the spec. The spec was written to be backwards compatible with those systems. Using the backwards compatibility option is correct if you wish to maintain backwards compatibility. Consider that Arch also technically violates Pep 394,

> for the time being, all distributions should ensure that python, if installed, refers to the same target as python2

We shouldn't update the shebangs in all of our software ever to accommodate a misbehaving, spec-non-compliant distro, should we?