John Mitchell-245523 (8/9/2016)
Do you still get the error if you try to remove the user like this?
DROP USER USERNAME
When trying to drop the required user using the above script, I get the following error message:
Msg 27226, Level 16, State 1, Procedure ddl_cleanup_object_permissions, Line 18
The database principal has granted or denied permissions to catalog objects in the database and cannot be dropped.
Msg 3609, Level 16, State 2, Line 3
The transaction ended in the trigger. The batch has been aborted.