fix: block non-instructor access to superset

Author: Ian2012

tutoraspects/templates/aspects/apps/superset/pythonpath/openedx_sso_security_manager.py

@@ -142,7 +142,7 @@ def get_courses(self, username, permission="staff", next_url=None):
             for course_id in next_courses:
                 courses.append(course_id)
 
-        return courses
+        raise Exception(f"User {username} is not an instructor")
 
 
 UserAccess = namedtuple("UserAccess", ["username", "is_superuser", "is_staff"])