Bug solved, circular conflict was due to not well installed PPA.
For replacing a xserver-xorg-video-intel from Ubuntu by one from PPA, Stefan Glasenhardt told me to do:
sudo apt-get -o Dpkg::Options::="--force-overwrite" dist-upgrade
instead of sudo apt-get upgrade.
It worked.
Bug solved, circular conflict was due to not well installed PPA. xorg-video- intel from Ubuntu by one from PPA, Stefan Glasenhardt told me to do: :="--force- overwrite" dist-upgrade
For replacing a xserver-
sudo apt-get -o Dpkg::Options:
instead of sudo apt-get upgrade.
It worked.