Now I've an error:
tux ~ # emerge --verbose-conflicts @preserved-rebuild
* IMPORTANT: 8 news items need reading for repository 'gentoo'.
* Use eselect news read to view new items.
Calculating dependencies... done!
[ebuild R ] dev-libs/botan-1.10.17
[ebuild U ] media-gfx/imagemagick-7.0.7.6 [6.9.9.0]
[ebuild R ] dev-python/pillow-4.2.1-r1
[ebuild U ] dev-qt/qtgui-5.9.2 [5.7.1-r1] USE="libinput* -vnc%"
[ebuild R ] media-video/ffmpeg-3.3.4
[ebuild U ] dev-qt/qtwidgets-5.9.2 [5.7.1] USE="gtk%*"
[ebuild U ] media-libs/gst-plugins-ugly-1.12.3 [1.10.5]
[ebuild U ] dev-qt/qtdeclarative-5.9.2 [5.7.1]
[ebuild U ] dev-qt/qtprintsupport-5.9.2 [5.7.1]
[ebuild U ] media-plugins/gst-plugins-x264-1.12.3 [1.10.5]
[ebuild U ] media-video/vlc-2.2.6-r2 [2.2.6] USE="qt5*"
[ebuild U ] dev-qt/qtwebchannel-5.9.2 [5.7.1]
[ebuild R ] net-analyzer/wireshark-2.4.2
[ebuild U ] xfce-base/xfwm4-4.13.0-r1 [4.12.3-r1] USE="opengl%*
-xpresent%"
[ebuild U ] app-editors/vim-8.0.1188 [8.0.0386] USE="terminal%*"
PYTHON_SINGLE_TARGET="python3_4%* -python2_7% -python3_5% -python3_6%"
[ebuild U ] dev-qt/qtwebengine-5.9.2 [5.7.1-r2]
[ebuild R ] dev-db/postgresql-9.6.5-r1
[ebuild U ] media-video/obs-studio-20.0.1-r1 [20.0.1]
[ebuild U ] net-print/cups-filters-1.17.9 [1.16.4] USE="-pclm%"
[ebuild U ] media-gfx/graphviz-2.40.1 [2.38.0-r1]
[ebuild R ] www-servers/nginx-1.12.1
[ebuild R ] dev-lang/php-7.0.24
[ebuild R ] dev-db/mariadb-10.2.9
!!! Multiple package instances within a single package slot have been pulled
!!! into the dependency graph, resulting in a slot conflict:
dev-qt/qtgui:5
(dev-qt/qtgui-5.7.1-r1:5/5.7::gentoo, installed) pulled in by
~dev-qt/qtgui-5.7.1 required by
(dev-qt/qtwebkit-5.7.1:5/5.7::gentoo, installed)
^
^
~dev-qt/qtgui-5.7.1[gles2=] required by
(dev-qt/qtopengl-5.7.1:5/5.7::gentoo, installed)
^
^
~dev-qt/qtgui-5.7.1 required by (dev-qt/qthelp-5.7.1:5/5.7::gentoo,
installed)
^
^
~dev-qt/qtgui-5.7.1[gles2=] required by
(dev-qt/qtprintsupport-5.7.1:5/5.7::gentoo, installed)
^
^
~dev-qt/qtgui-5.7.1 required by
(dev-qt/qtquickcontrols-5.7.1:5/5.7::gentoo, installed)
^
^
~dev-qt/qtgui-5.7.1[gles2=] required by
(dev-qt/qtmultimedia-5.7.1:5/5.7::gentoo, installed)
^
^
~dev-qt/qtgui-5.7.1[gles2=,png=,xcb?] required by
(dev-qt/qtwidgets-5.7.1:5/5.7::gentoo, installed)
^
^
~dev-qt/qtgui-5.7.1[gles2=] required by
(dev-qt/qtdeclarative-5.7.1:5/5.7::gentoo, installed)
^
^
~dev-qt/qtgui-5.7.1 required by (dev-qt/qtsvg-5.7.1:5/5.7::gentoo,
installed)
^
^
~dev-qt/qtgui-5.7.1[xcb] required by
(dev-qt/qtx11extras-5.7.1:5/5.7::gentoo, installed)
^
^
(dev-qt/qtgui-5.9.2:5/5.9::gentoo, ebuild scheduled for merge) pulled
in by
~dev-qt/qtgui-5.9.2[gles2=,png=,xcb?] required by
(dev-qt/qtwidgets-5.9.2:5/5.9::gentoo, ebuild scheduled for merge)
^
^
~dev-qt/qtgui-5.9.2[gles2=] required by
(dev-qt/qtdeclarative-5.9.2:5/5.9::gentoo, ebuild scheduled for merge)
^
^
~dev-qt/qtgui-5.9.2 required by
(dev-qt/qtwebengine-5.9.2:5/5.9::gentoo, ebuild scheduled for merge)
^
^