Set the sentry_dsn for travis, if not set in environment.
Set the sentry_dsn for travis, if not set in environment.

Resolves #447

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