Missing details

Sure there are some immediate issues (such as print and division) but these have been around for some time:
- the use of the -3 flag (Python 2.6)
- usage of 'from __future__ import' ('from __future__ import division' was Python 2.2 - 2002!)
Also Python 2.7 has brought more attention than Python 2.6 to need to migrate.

However, I think there are two bigger issues involved. One for developers has been the API changes because many Python 2.x projects often used depreciated functions that were removed for Python 3.

The second is the far more important is which Linux distributions are providing Python 3.x as the default Python?
While you can build Python 3 yourself or have it as secondly package in recent distros, you can not use it as default without disrupting any Python 2.x code especially system related code.