Well, because you're developing against an unsupported runtime. No bug or security updates. If that's fine for you, feel free, otherwise get with the (supported) program.
If it's a new project, there are no excuses imho
If it's a new project, there are no excuses imho
http://python-future.org/automatic_conversion.html and https://python-modernize.readthedocs.io/en/latest/
Which should get you most of the way there. Look at https://docs.python.org/3/howto/pyporting.html for more info