defun with find-file does not run from Gnus buffers

[Albert Reiner]

Hi,

I wanted to have a shortcut for opening a specific file, so I wrote
the following function:

    (defun willehalm-note ()
       (interactive "*")
       (find-file "~/.once-to-willehalm/note"))

This works well from most buffers I use; however, when I do M-x
willehalm-note in a Gnus (*Group*, *Summary ...*, *Article*) buffer, I
get a message about the buffer being read-only:

,----
| Buffer is read-only: #<buffer *Summary nntp+news.gnus.org:gnu.emacs.help*>
`----

While this is true, I don't quite see why that should matter as
willehalm-note shouldn't write anything to any buffer.

I hope someone will point me to the reason underlying this behavior,
and to a cure for my defun.  (I suppose a keyboard macro would not
have that problem, but I'll probably learn more about elisp that way.)

TIA,

Albert.