Common error message for psql

## Communication goals (e.g. detailed howto vs orientation)

People get confused by this error:

```
psql: could not translate host name "example.com" to address: nodename nor servname provided, or not known
```

It just means that the DNS doesn't resolve to an IP address. Provide a suggestion to verify:

```
dig example.com A +short
```

Note that resolving host with a closed port gives a different error:

```
psql: could not connect to server: Operation timed out
Is the server running on host "example.com" (192.0.2.0) and accepting
TCP/IP connections on port 9999?
```

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