> Correct.  We can't touch Python 3.1, 2.6, or earlier because those are all in
> security-only mode, and unless a specific security related issue is
> identified, the change should not be made there.  That's just life (a recent
> similar example is support for multiarch in newer Debian and Ubuntu releases -
> we just don't support that in security-only Pythons).
> 
> We can and should change Python 3.2 and 2.7 to only report 'linux2' for
> backward compatibility.

It means someone upgrading from 2.6 to 2.7 will see sys.platform change
from "linux3" to "linux2". That breaks compatibility.

> For Python 3.3, we should do the right thing, which IMO is to set sys.platform
> to 'linux' without the version number.  In parallel we can change the stdlib
> tests to use .startswith() and encourage third party developers to use
> .startswith() also.

The latter is already done in the documentation.