Is really not that hard to make C extension support Python 3, you're either using an extension that is no longer maintained, or its author(s) are stubborn, which is a different kind of problem.
Making code compatible with python2.7 onward means that you can't use any new features from 3+ and the code is plain ugly, I don't know if you wrote 2/3 compatible code, it is not as enjoyable to do.
I think Django's approach where the LTS will still work on 2.7 (and LTS is for 3 years, which is until python2 itself stop being maintained) is fair.
You still have 3 years to fix things and if you want to use latest Django and be cutting edge, you probably should use latest Python as well.
Making code compatible with python2.7 onward means that you can't use any new features from 3+ and the code is plain ugly, I don't know if you wrote 2/3 compatible code, it is not as enjoyable to do.
I think Django's approach where the LTS will still work on 2.7 (and LTS is for 3 years, which is until python2 itself stop being maintained) is fair.
You still have 3 years to fix things and if you want to use latest Django and be cutting edge, you probably should use latest Python as well.