Upgrade Django to 1.8.15
Upgrade Django to 1.8.15

Livit/Livit.Learn.EdX,mbareta/edx-platform-ft,Livit/Livit.Learn.EdX,Livit/Livit.Learn.EdX,marcore/edx-platform,Livit/Livit.Learn.EdX,mbareta/edx-platform-ft,marcore/edx-platform,mbareta/edx-platform-ft,marcore/edx-platform,mbareta/edx-platform-ft,marcore/edx-platform