pre-commit: black: --target-version py35

[blueyed]

This is meant to avoid having trailing commas after **kwargs, which
only works in Python 3.5.2+.

Ref: 2e756d698, #5611

Might make more sense to add config for it: blueyed#275

[blueyed]

What about using a config instead?

Might make more sense to add config for it: blueyed#275

[blueyed]

I assume this will make it work better out of pre-commit also.

But likely I was just being "tricked" by having added trailing commas myself, and then black does not remove them (I guess).

[bluetech]

Config file would be better, this way editors will be able to catch it as well.