A nightly pg_dump that fails with the reason, not with "Network is unreachable"

Munchable's Postgres runs on a hosted tier that provides no managed backups. That makes a nightly GitHub Actions job the only line of defence against data loss, so the workflow is intentionally simple and loud: pg_dump to Cloudflare R2, and if it fails, the platform emails the repo admins. This post is about the checks that were added to it 27...