PEP 515: Underscores in Numeric Literals

[moto-timo]

https://docs.python.org/3.6/whatsnew/3.6.html#pep-515-underscores-in-numeric-literals

https://www.python.org/dev/peps/pep-0515

https://docs.python.org/3.6/library/string.html#formatspec