remove manual installation of python-psutil since its been allowed by travis apt plugin
remove manual installation of python-psutil since its been allowed by travis apt plugin

learningequality/installers,learningequality/installers,ruimalheiro/installers,learningequality/installers,learningequality/ka-lite-installers,benjaoming/installers,mrpau/installers,learningequality/ka-lite-installers,benjaoming/installers,mrpau/installers,benjaoming/installers,learningequality/ka-lite-installers,benjaoming/installers,learningequality/ka-lite-installers,ruimalheiro/installers,mrpau/installers,ruimalheiro/installers,ruimalheiro/installers,mrpau/installers,learningequality/installers