On Oct 15, 2014, at 10:47 PM, Stefan Monnier wrote:

>The real underlying cause is dpkg's inability to handle simultaneous
>installs of different versions of the same package.  As a result, you
>get more work, as you point out, and I can't easily keep around all the
>versions I'd like to keep.

It depends.  We can install multiple different versions of Python
simultaneously, including both Python 2[*] and Python 3, but it took a lot of
work both in upstream and in Debian by the Python maintainers to make that
happen.

Cheers,
-Barry

[*] Although we only care about Python 2.7 now.