Ray, I forked your repository, incorporated my changes to ospi_gc.py to support apiv3 (among other enhancements) and issued a pull request to you. I will try and do the same thing for sprinklers_pi.
My longer term vision for the google calendar integration would to be to 1) cache locally and check a few times per day rather than polling every 60 seconds, and 2) use it to trigger a program in sprinklers_pi or the interval program rather than directly control zones.
-Jason