Update TokenAdmin to respect USERNAME_FIELD of the user model.

Author: m000

rest_framework/authtoken/admin.py

@@ -24,7 +24,6 @@ def url_for_result(self, result):
 class TokenAdmin(admin.ModelAdmin):
     list_display = ('key', 'user', 'created')
     fields = ('user',)
-    search_fields = ('user__username',)
     search_help_text = _('Username')
     ordering = ('-created',)
     actions = None  # Actions not compatible with mapped IDs.
@@ -45,6 +44,13 @@ def get_object(self, request, object_id, from_field=None):
         except (queryset.model.DoesNotExist, User.DoesNotExist, ValidationError, ValueError):
             return None
 
+    def get_search_fields(self, request):
+        if hasattr(self, 'search_fields'):
+            return self.search_fields
+        user_model = Token._meta.get_field('user').related_model
+        username_lookup = 'user__%s' % user_model.USERNAME_FIELD
+        return (username_lookup,)
+
     def delete_model(self, request, obj):
         # Map back to actual Token, since delete() uses pk.
         token = Token.objects.get(key=obj.key)