Nonexistent processes and groups passed to `supervisortctl status` are
printed to STDOUT as follows:
```
$ supervisorctl status zulip-django nonexistent-process nonexistent-group:*
nonexistent-process: ERROR (no such process)
nonexistent-group: ERROR (no such group)
zulip-django RUNNING pid 16043, uptime 17:31:31
```
On supervisor 4 and above, this exits with an exit code of 4;
previously, it returned exit code 0. Ubuntu 18.04 has version 3.3.1,
and Ubuntu 20.04 has version 4.1.0.
Skip any lines with `ERROR (no such ...)`, and accept exit code 4 from
`supervisorctl status`.
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