Enable error logging with Sentry

[di]

Partially done in #163, but requires a migration to gen2 functions (#164), which can't just be deployed over existing functions for some reason:

Step #1: ERROR: (gcloud.functions.deploy) Invalid value for [--gen2]: Function already exists in 1st gen, can't change the environment.

Which requires either an entirely new function name, or the function to be deleted/recreated: https://stackoverflow.com/a/73821391

[di]

This seems to be working as-is! https://python-software-foundation.sentry.io/issues/?project=63744