Qt4 is dead and going away.
https://github.com/bistromath/gr-air-modes/blob/master/apps/modes_gui Looks like it uses qt4. You could just disable GUI support if you want to kill qt4 in the tree.
In fact, this package is broken already since it missed to depend on PyQt4[qtwebkit] which is gone for a long time.
The bug has been closed via the following commit(s): https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=6d40df5d65ef598071ea49571143013d762dcff7 commit 6d40df5d65ef598071ea49571143013d762dcff7 Author: Andreas Sturmlechner <asturm@gentoo.org> AuthorDate: 2018-03-04 12:17:10 +0000 Commit: Andreas Sturmlechner <asturm@gentoo.org> CommitDate: 2018-03-04 12:38:10 +0000 net-wireless/gr-air-modes: Drop broken USE=gui Closes: https://bugs.gentoo.org/649220 Package-Manager: Portage-2.3.24, Repoman-2.3.6 net-wireless/gr-air-modes/gr-air-modes-9999.ebuild | 5 ++--- net-wireless/gr-air-modes/metadata.xml | 1 - 2 files changed, 2 insertions(+), 4 deletions(-)