This should make Python updates easier.

MAINT use variables for Python version rather than hardcoding it. This should make Python updates easier.

[flake8]
extend-ignore = E203, E402, E501, E731, E741, B950
select = C,E,F,W,B,B9

[flake8]
extend-ignore = E203, E402, E501, E731, E741, B950
select = C,E,F,W,B,B9
