This request prompted me to do a good bit of work: first, to solve this specific issue and second to think through a pattern that others can use to make other AppleScriptable apps available to Indigo Python scripts.
The result is the
Indigo Reminders AppleScript. At it's easiest, it's an AppleScript that you can call from an Indigo Python script to create, complete, and delete reminders in the macOS Reminders App. The link takes you to the wiki which is hosted on Github and tells you how to use the script. I decided to host it on Github so that others can contribute changes/modifications/bug fixes if you're so inclined, but also so that the non-technical users can contribute to the documentation.
Use this thread if you need help using it (I'm going to put a link from the first post to this one so people can easily get to the solution.