1. Modify `update_user_avatar` endpoint to throw `ServerError` (we can't just kill `keyserver` because we want to make sure the alert is triggered by the `update_user_avatar`-specific codepath which we modified).
2. Try to set a user image avatar via "Camera" flow
3. Ensure that I see expected Alert.
Also, make sure the "happy case" (unmodified `update_user_avatar` endpoint) continues working as expected).
WARNING: I haven't actually gone through the Test Plan yet, will sequence at the end of all of the refactors and **definitely** before landing.