Another problem arise while I tried to restore a backup of some database and try to remove the user ASPNET. After ‘googlear’ I found with the entry of blog of Kaushal where explain how to solve this issue.
After fix it, other error message was show which doesn’t allow me delete an user of database (ASPNET), the message was similar to previous. This was: The database principal owns a database role and cannot be dropped.
To fix the last error, I follow the same steps which I used to previous error, but I look for Roles instead of Schemas, and then I changed the owner from ASPNET to dbo