Comment 18 for bug 1834974

so, I have tried the QA from @mandart 's PR https://github.com/juju/juju/pull/10288 and indeed it's failing now on 2.9.46. The problem seems to be the sshInstanceConfigurator that's failing to change or read iptables' rules and this kills the firewaller worker over and over:

```
machine-0: 18:52:15 ERROR juju.worker.dependency "firewaller" manifold worker returned unexpected error: cannot respond to units changes for "machine-0", "90d83707-6a90-48f5-850f-f1599433d42b": configuring ports for address "": : subprocess encountered error code 255
machine-0: 18:54:21 ERROR juju.worker.dependency "firewaller" manifold worker returned unexpected error: cannot respond to units changes for "machine-1", "90d83707-6a90-48f5-850f-f1599433d42b": configuring ports for address "": : subprocess encountered error code 255
machine-0: 18:56:23 ERROR juju.worker.dependency "firewaller" manifold worker returned unexpected error: cannot respond to units changes for "machine-0", "90d83707-6a90-48f5-850f-f1599433d42b": configuring ports for address "": : subprocess encountered error code 255
```

I'm going to investigate.