Granting cron permission to control Finder

I aim to use cron to call a python script that changes my desktop background. The key python line is as follows:

from appscript import mactypes, app
app('Finder').desktop_picture.set(mactypes.File(chosen_pic))

When running said script from Terminal, the program runs, but when called by cron, this line gives an error that appears via mail. Experimentation yielded that running from Terminal gives the same error when its permission to edit Finder is unchecked here:

It seems likely that if I could give cron permission to control Finder in this way, that’d solve the problem, but cron’s not on this list, and I don’t see a way to add it. By contrast, the Full Disk Access pane lets one add new programs, but adding cron doesn’t solve this. If it helps, this is on Catalina 10.15.5.

How can one add a new app to the Automation pane here and give it permission to control another app?

Thank you!