When starting the worker, we now check the Python version. If it's

Python 2, we warn that Python 2 and Celery 3 are no longer supported and

may have security risks, recommending an upgrade to Python 3.
If running on Python 3, we show the Python and Celery versions (as a

reference) and have a general recommendation to keep up with versions.

Tested running under Python 2 and 3, checking the resulting output

and version numbers.