Replaces unittest with unittest2 if it's available
Replaces unittest with unittest2 if it's available

celiafish/VisTrails,hjanime/VisTrails,minesense/VisTrails,hjanime/VisTrails,celiafish/VisTrails,Nikea/VisTrails,hjanime/VisTrails,VisTrails/VisTrails,minesense/VisTrails,hjanime/VisTrails,Nikea/VisTrails,VisTrails/VisTrails,minesense/VisTrails,VisTrails/VisTrails,minesense/VisTrails,celiafish/VisTrails,celiafish/VisTrails,minesense/VisTrails,hjanime/VisTrails,Nikea/VisTrails,VisTrails/VisTrails,Nikea/VisTrails,VisTrails/VisTrails