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

Calculating dependencies... done!

!!! The ebuild selected to satisfy ">=media-sound/gnome-music-3.24.2" has unmet requirements.
- media-sound/gnome-music-3.24.2::gentoo USE="" ABI_X86="(64)" PYTHON_SINGLE_TARGET="-python3_4 -python3_5" PYTHON_TARGETS="-python3_4 -python3_5"

  The following REQUIRED_USE flag constraints are unsatisfied:
    exactly-one-of ( python_single_target_python3_4 python_single_target_python3_5 )

  The above constraints are a subset of the following complete expression:
    exactly-one-of ( python_single_target_python3_4 python_single_target_python3_5 ) python_single_target_python3_4? ( python_targets_python3_4 ) python_single_target_python3_5? ( python_targets_python3_5 )

(dependency required by "gnome-base/gnome-extra-apps-3.24.2::gentoo[tracker]" [installed])
(dependency required by "gnome-base/gnome-3.24.2::gentoo[extras]" [installed])
(dependency required by "@selected" [set])
(dependency required by "@world" [argument])