Signed-off-by: Dan Callahan <danc@element.io>

This allows trailing commas in multi-line arg lists.

Minor, but we might as well keep our formatting current with regard to
our minimum supported Python version.

Signed-off-by: Dan Callahan <danc@element.io>

... and certain other changelog-related fixes

* Add a few more common environment directory names to black exclusion

* Add changelog