bug in Ubuntu Human theme?

[The Saltydog]

After a long discussion in perl-gtk2 mailing list, muppet (one of the
authors of Perl-Gtk2) has ended with the decision that the Human theme
in ubuntu has a bug.
Here is his last message:

"It's a bug in your theme, then.  That text string appears nowhere in the gtk+
source, nor in the gtk2-perl source.
The widget parameter to paint_box() is used by the theme implementation to get
hints, either from style properties or from the type of the object itself.
The "what sort of box" hint is the string "trough", and my guess is that your
theme's implementation of paint_box() thinks that a "trough" will only be
drawn for a GtkRange."