Django REST Framework has an excellent piece of documentation about permissions. I\'ve been able to use pre-made permission classes and also built my own.
However, there
By default, it is handled by default exception handler, and it is raising a standard message - https://github.com/tomchristie/django-rest-framework/blob/2eb9107b875972e442ed73eef0e653fd4480d873/rest_framework/views.py#L82
But, you can set own EXCEPTION_HANDLER
in settings of DRF, and handle PermissionDenied
exception to return message you want.
See description at http://www.django-rest-framework.org/api-guide/settings/