There is an updated pull request by abenson against master on the void-packages repository

https://github.com/abenson/void-packages aniso8601-7
https://github.com/void-linux/void-packages/pull/12603

python3-aniso8601: update to 7.0.0.


A patch file from https://github.com/void-linux/void-packages/pull/12603.patch is attached