Add test for trying to create a course with a duplicate slug
Add test for trying to create a course with a duplicate slug

MusikAnimal/WikiEduDashboard,sejalkhatri/WikiEduDashboard,WinnySilva/WikiEduDashboard,sejalkhatri/WikiEduDashboard,KarmaHater/WikiEduDashboard,WikiEducationFoundation/WikiEduDashboard,adamwight/WikiEduDashboard,majakomel/WikiEduDashboard,adamwight/WikiEduDashboard,WikiEducationFoundation/WikiEduDashboard,KarmaHater/WikiEduDashboard,feelfreelinux/WikiEduDashboard,majakomel/WikiEduDashboard,KarmaHater/WikiEduDashboard,Wowu/WikiEduDashboard,Wowu/WikiEduDashboard,feelfreelinux/WikiEduDashboard,feelfreelinux/WikiEduDashboard,MusikAnimal/WikiEduDashboard,ragesoss/WikiEduDashboard,WinnySilva/WikiEduDashboard,WinnySilva/WikiEduDashboard,Wowu/WikiEduDashboard,sejalkhatri/WikiEduDashboard,alpha721/WikiEduDashboard,feelfreelinux/WikiEduDashboard,MusikAnimal/WikiEduDashboard,alpha721/WikiEduDashboard,alpha721/WikiEduDashboard,alpha721/WikiEduDashboard,ragesoss/WikiEduDashboard,sejalkhatri/WikiEduDashboard,WikiEducationFoundation/WikiEduDashboard,ragesoss/WikiEduDashboard,sejalkhatri/WikiEduDashboard,majakomel/WikiEduDashboard,MusikAnimal/WikiEduDashboard,WikiEducationFoundation/WikiEduDashboard,Wowu/WikiEduDashboard,adamwight/WikiEduDashboard,majakomel/WikiEduDashboard,WikiEducationFoundation/WikiEduDashboard,KarmaHater/WikiEduDashboard