Fix mistake.

biscuit/core/decorators.py

@@ -12,5 +12,5 @@ def teacher_required(function=None):
 
 
 def admin_required(function=None):
-    actual_decorator = user_passes_test(lambda u: u.is_active and u.is_admin)
+    actual_decorator = user_passes_test(lambda u: u.is_active and u.is_superuser)
     return actual_decorator(function)