Introducing python3 into user system

[Mark Linimon]

On Mon, Oct 17, 2016 at 01:35:45PM +0300, Ruslan Makhmatkhanov wrote:
> Ok, PHB was just an example. But it should be some "authoritative" place to
> encourage people to change their ports and to prevent adding of new ports
> without specific python version set (I still see many new ports added with
> just USES=python, while it may not build with python3 at all).

Although I'm the first to acknowledge that our wiki is a mess, this seems
like an appropriate use of it.

Please contact me off-line if you want help with that task.

mcl