I was not affected by Py3 at all. First I completely ignored it for five years while it gestated. Then started kicking the tires when 3.4 dropped on a LTS. When 3.6 with better dicts and f-strings landed I moved over with barely a whimper, since I'd had a decade to get things upgraded to 2.7 first.
None of my projects needed to worry much about char encoding, and I'd used logging extensively starting under 2.6 or so.
Porting your own code was relatively easy. The problem was porting all your dependencies, and replacing the ones that were abandoned and didn't support 3.x.
They were ready long before 3.6, sqlalchemy added support for Python 3.1 in 0.6, and Django 1.5 introduced support for Python 3.2 on an experimental basis with 1.6 removing the “experimental” bit.
None of my projects needed to worry much about char encoding, and I'd used logging extensively starting under 2.6 or so.