py3.8

Build the docs with Python 3.8.

>>> # Use walrus operator available in Python3.8
>>> import random
>>> while number := random.choice(range(10)):
...     print(number)
... 

>>> # Build at
>>> import datetime
>>> datetime.datetime.utcnow()  # UTC
datetime.datetime(2020, 2, 25, 17, 21, 55, 822058)