Google Calendar API update compatible with Appointments + ?

My google account does not seem to give me a .p12 file only a json file. So when I follow all the steps to setup appointments+ and integrate with Google Calendar using the api then test it, just complains that there is no key file.

According to Google, they are depreciating the old methods in favor of json, but Appointments+ shows nothing on how to deal with this. Am I supposed to go follow Google's instructions for migrating depreciated clients to the new system?