bug#32989: 26.1; Opening PDF attachments in Gnus with doc-view-mode causes error on Windows

[Eli Zaretskii]

> From: Jordan Wilson <jordan.t.wilson@gmx.com>
> Date: Mon, 08 Oct 2018 15:44:55 +0100
> 
>   File error: "Opening output file", "Invalid argument", 
> "c:/Users/Jordan/Emacs/.cache/docview-cache/ *mm*-012345" 
> 
> this leaves a buffer showing the file literally. If I rename that buffer
> to something not containing an asterisk, it displays fine when running
> "doc-view-mode". Windows apparently can't handle asterisks in
> directory/file names.

Windows doesn't allow '*' (and a few other characters) in any file
name, not just in directory name.  Gnus should run the file name
through convert-standard-filename to get something that is guaranteed
to work on any filesystem.