Brett Cannon - Why Python 3 exists
www.snarky.ca/why-python-3-exists
From the page
Saved with the link. Notes from 2007 to 2016 are mostly the page's own words, so this is probably an excerpt.
And it's the fact that there are two correct answers in Python 2 for what the str object represents that led to changing the language so that the single Python 3 answer was the only answer.