Hi,

BUG-1:
If a group for a certain bug number is once read and its contents
are cached, the following error happens.  This is the case I do

M-x gnus-read-ephemeral-emacs-bug-group RET 26862 RET

for reading bug#26862.

Debugger entered--Lisp error: (file-error "https://debbugs.gnu.org/cgi/bugreport.cgi?bug=26862;mboxmaint=yes;mboxstat=yes" "Not modified")
  signal(file-error ("https://debbugs.gnu.org/cgi/bugreport.cgi?bug=26862;mboxmaint=yes;mboxstat=yes" "Not modified"))
  url-insert-file-contents("https://debbugs.gnu.org/cgi/bugreport.cgi?bug=26862;mboxmaint=yes;mboxstat=yes")
  gnus-read-ephemeral-bug-group((26862) "https://debbugs.gnu.org/cgi/bugreport.cgi?bug=%s;mboxmaint=yes;mboxstat=yes" nil)
  gnus-read-ephemeral-emacs-bug-group(26862)

It's not intentional, is it?  Fixing it is easy by passing t as
the second argument to `url-insert-file-contents'.  However, it
causes another problem; the program prompts me for the yes-or-no
query when I redo `M-x gnus-read-ephemeral-emacs-bug-group' as:

Buffer  *temp file* modified; kill anyway? (yes or no)

This happens when finishing the (with-temp-file ...) form because
`url-insert-file-contents' sets `buffer-file-name' as the second
argument is set.  So, `buffer-file-name' has to be reset to nil.


BUG-2:
An example that (info "(gnus)Foreign Groups") introduces

   Here is an example:
     (require 'gnus-art)
     (add-to-list
      'gnus-button-alist
      '("#\\([0-9]+\\)\\>" 1
        (string-match "\\<emacs\\>" (or gnus-newsgroup-name ""))
        gnus-read-ephemeral-emacs-bug-group 1))

passes a bug number to `gnus-read-ephemeral-emacs-bug-group' as
a string.  Even if BUG-1 is fixed, this causes a bug as follows:

Debugger entered--Lisp error: (wrong-type-argument numberp "26862")
  number-to-string("26862")
  mapconcat(number-to-string ("26862") ",")
  gnus-read-ephemeral-bug-group(("26862") "https://debbugs.gnu.org/cgi/bugreport.cgi?bug=%s;mboxmaint=yes;mboxstat=yes" nil)
  gnus-read-ephemeral-emacs-bug-group("26862")

A patch for both the bugs is below.  Thanks.

In GNU Emacs 26.0.90 (build 1, i686-pc-cygwin, GTK+ Version 3.18.9)
 of 2017-10-26 built on localhost
Windowing system distributor 'The Cygwin/X Project', version 11.0.11900000


* lisp/gnus/gnus-group.el (gnus-read-ephemeral-gmane-group)
(gnus-read-ephemeral-bug-group): Make it work for any number of times.
(gnus-read-ephemeral-emacs-bug-group): Allow a string for bug#.