the author of the package here. This was mostly an experiment to see how to upload packages to PyPi myself. I am unsure why it broke or if it ever even worked properly in the first place. Regardless, I took the time to fix it and reupload it to PyPi.
You should now be able to pip install isacalc
and use the library as-is.
I also did some refactoring.
Cheers!