Should `python` point to python3?

[jonringer]

@raboof

In the mean time, for packages that work with both python2 and python3, should we:

• change the derivation to expect python3 rather than python , or
• keep python in the derivation and pass python = python3 in all-packages.nix ?

I have a preference toward referring to python3 explicitly. It makes it easier to grep for references to just python