Replace group with static username

openedx/core/djangoapps/user_api/accounts/permissions.py

@@ -3,6 +3,7 @@ Permissions classes for User accounts API views.
 """
 from __future__ import unicode_literals
 
+from django.conf import settings
 from rest_framework import permissions
 
 USERNAME_REPLACEMENT_GROUP = "username_replacement_admin"
@@ -31,4 +32,4 @@ class CanReplaceUsername(permissions.BasePermission):
     including the service user.
     """
     def has_permission(self, request, view):
-        return request.user.groups.filter(name=USERNAME_REPLACEMENT_GROUP).exists()
+        return request.user.username == getattr(settings, "USERNAME_REPLACEMENT_WORKER")