bug#53070: 27.2; Message "Server closed connection" not verbose enough

[Tim Landscheidt]

I have a number of IMAP, POP3 and NNTP servers configured.
When everything is fine, gnus-group-get-new-news will output
the messages:

| Checking new news...
| Reading active file from private via nnml...
| Reading incoming mail from pop... [3 times]
| Reading incoming mail from file...
| nnml: Reading incoming mail (no new mail)...done
| Reading active file from private via nnml...done
| Reading active file from archive via nnfolder...done
| Reading active file via nndraft...done
| Checking new news...done

>From time to time, there will be a hiccup somewhere, and the
messages instead will read:

| Checking new news...
| Opening connection to imap.gmail.com via tls...
| Opening connection to imap.gmail.com...done
| Reading active file from private via nnml...
| Reading incoming mail from pop...
| pop3 retrieved 0KB (0%) [14 times]
| pop3 retrieved 16KB (17%) [10 times]
| pop3 retrieved 32KB (35%) [20 times]
| pop3 retrieved 49KB (53%) [10 times]
| pop3 retrieved 65KB (71%) [10 times]
| pop3 retrieved 81KB (89%) [8 times]
| pop3 retrieved 91KB (100%)
| Wrote /path/to/nnml/file
| Reading incoming mail from pop... [2 times]
| Reading incoming mail from file...
| nnml: Reading incoming mail (1 new)...done
| Reading active file from private via nnml...done
| Reading active file from archive via nnfolder...done
| apply: Server closed connection

Now "Server closed connection" is an error message defined
for IMAP /and/ NNTP servers, and I have configured more than
one NNTP server as well.  So I had to set
nntp-record-commands to t and look in *nntp-log*'s:

| 20220106T154438.490 news.gmane.io MODE READER
| 20220106T154508.531 news.gmane.io *** CONNECTION LOST ***
| 20220106T154511.955 news.gmane.io MODE READER
| 20220106T154541.984 news.gmane.io *** CALLED nntp-report ***

to /assume/ that the error occurs while Gnus is trying to
talk to news.gmane.io.

It would be more helpful if the error message read "Server
news.gmane.io closed connection" or, to avoid any ambiguity,
"NNTP server news.gmane.io closed connection".

(Side note: If such a hiccup happens, it sometimes appears
that the *Group* buffer is not updated with regard to number
of unread messages per group, etc. for /other/ servers that
were successfully contacted.  I don't know if Gnus is more
aggressive than it needs to be here; if it encounters an er-
ror when trying to contact a POP3 server, it will just ask
nicely and continue on.)