[Nut-upsdev] usbmon fails silently to start with invalid RUN_AS_USER values

[Håkon Løvdal]

Hi. I have an improvement suggestion.

Say that a careless user starts editing upsmon.conf before having read
the complete documentation (not that I know of any such users of course)
and starts by adding "RUN_AS_USER = nutmon" and then creates this user.
Later he discovers that the rpm package already has created a "nut" user
and therefore deletes the nutmon user but forgets to update upsmon.conf.

In this case usbmon will fail silently to start up, without any clues why.
Please add some code to usbmon to output a descriptive error
message in this case.

BR Håkon Løvdal