Ansible only works with 2.x, so that is perhaps the only exception I would make... (if you are an ansible shop).

But ansible scripts tend to be like 5 lines, so it is not the same as the scale you would write a webapp or something in Python3...

For Ansible, it's important to differentiate between the master and client side code.

Client side code has to run on everything starting with CentOS 6, so they have to stick with Python 2 for a long time.

For the Ansible master (which runs on the management machine), Python 3 porting work is already underway.

We're a Python shop but all of our Ansible work is just YAML. Ansible is a program more than a library so it's almost irrelevant what version of Python they use. Now, of course it's highly annoying to have to bootstrap python2 on Ubuntu Xenial but that's really not relevant to what version of Python a group uses for regular development.

We use Python 3.5 and are VERY happy about it.