They read this, or you show it to them: Should I use Python 2 or Python 3 for my development activity? https://wiki.python.org/moin/Python2orPython3
It starts off very encouraging: "Short version: Python 2.x is legacy, Python 3.x is the present and future of the language"
Then we skim down to the meat of the page: Which version should I use?
Two short version stating that 3 is great, and you should use it. If you can.
And about 20 paragraphs of caveats.
To the person who's been around the block once or twice, or doesn't want to be seen as that pie in the sky programmer to his boss whose focus is not programming and doesn't give a shit about new, what stands out is "you can use virtually every resource available in 2, and almost mostly totally in 3 also."
And if you're new in any sense, do you really want to spend the time researching if 3 is going to work for you or your group/boss/career? No, you pick 2 and GSD.
When that page is gone, or its caveats are substantially reversed, 3 will be the choice.