[MERGE] setup.py script explicitly checks for Python version. (#200569)

[Alexander Belchenko]

John Arbash Meinel пишет:
> Alexander Belchenko wrote:
> | Currently there is python reinvocation logic in setup.py, but it's
> | actually useless,
> | as bug #200569 reveals. The patch removes this logic and provide
> | explicit check for
> | Python version before import bzrlib.
> |
> | I think it's worth to merge to bzr.dev.
> |
> 
> BB:tweak
> 
> I think we should use sys.version_info rather than sys.hexversion

I don't think so. Paranoid in me said in this case we should use try-except.
Why for? sys.hexversion do the same thing and code less.

> 
> All you really need to do is move the existing check earlier (and I 
> would get
> rid of the REINVOKE stuff).
> 
> John
> =:->