These are the packages that would be merged, in order:

Calculating dependencies ... done!
Dependency resolution took 0.85 s (backtrack: 0/20).


The following USE changes are necessary to proceed:
 (see "package.use" in the portage(5) man page for more details)
# required by gnome-base/dconf-editor-45.0.1::gentoo
# required by =gnome-base/dconf-editor-45.0.1 (argument)
>=gui-libs/libhandy-1.8.3 vala

!!! The ebuild selected to satisfy ">=gui-libs/libhandy-1.6.0:1[vala]" has unmet requirements.
- gui-libs/libhandy-1.8.3::gentoo USE="-examples -glade -gtk-doc -introspection -test -vala"

  The following REQUIRED_USE flag constraints are unsatisfied:
    vala? ( introspection )

  The above constraints are a subset of the following complete expression:
    gtk-doc? ( introspection ) vala? ( introspection )

(dependency required by "gnome-base/dconf-editor-45.0.1::gentoo" [ebuild])
(dependency required by "=gnome-base/dconf-editor-45.0.1" [argument])