Gtk-WARNING from file chooser

[Robert Pearce <rob bdt-home demon co uk>]

Hello most excellent experts!

I have an application from which I can save several types of files.
When the user wants to save something I use a Gtk::FileChooserDialog to
allow her to pick a file name. Since this is a save operation I
construct this with the Gtk::FILE_CHOOSER_ACTION_SAVE parameter.

Now, suppose the user wants to create a brand new shiny file that
doesn't overwrite her previous results. Seems like exactly what this
option is supposed to allow. So why do I get:

(vpctrl:22603): Gtk-WARNING **: Unable to retrieve the file info for `file:///home/rob/OVS/newLogger5.csv': Error stating file '/home/rob/OVS/newLogger5.csv': No such file or directory

It's a new file. It was chosen in a "save as..." dialog. Why would Gtk
want to try "stating" it? And even if it does, why produce a warning
for what must surely be the most common expected condition?

Yours mildly mystified,
Rob