Comment 1 for bug 1883859

This also happened on charm-nova-cloud-controller. See:
"""
2020-06-17 09:03:23 DEBUG cloud-compute-relation-changed dns.resolver.NoNameservers: All nameservers failed to answer the query vm4. IN A: Server 127.0.0.53 UDP port 53 answered SERVFAIL
2020-06-17 09:03:23 ERROR juju.worker.uniter.operation runhook.go:136 hook "cloud-compute-relation-changed" (via explicit, bespoke hook script) failed: exit status 1
"""

The ERROR level only says that the hook failed, while the DEBUG level says why (+ a python traceback).