Stop writing Python 4 incompatible code

[Gregory Ewing]

Chris Angelico wrote:
> and 3.X would wreak havoc with people's heads.

The danger there is that 3.X would sound so cool (everything
is cooler with an X in it) that nobody would want to move
past it. So after 3.X we would get 3.X.1, ... and then
3.X.X.1, ...

At some point people would start abbreviating those in terms
of powers of X, so the general format of a version number
would become 3.X**m.n where 0 <= n < X.

-- 
Greg