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

Calculating dependencies ... done!
Dependency resolution took 0.91 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 net-misc/rygel-46.0::gentoo
# required by =net-misc/rygel-46.0 (argument)
>=net-libs/gupnp-1.6.10 vala
# required by net-misc/rygel-46.0::gentoo
# required by =net-misc/rygel-46.0 (argument)
>=net-libs/gssdp-1.6.6 vala

!!! The ebuild selected to satisfy ">=net-libs/gssdp-1.5.0:1.6=[vala]" has unmet requirements.
- net-libs/gssdp-1.6.6::gentoo USE="-gtk -gtk-doc -introspection (-man) -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 "net-misc/rygel-46.0::gentoo" [ebuild])
(dependency required by "=net-misc/rygel-46.0" [argument])