WP_Error $errors, string $sanitized_user_login, string $user_email )
Filters the errors encountered when a new user is being registered.
If any errors are present in $errors, this will abort the user’s registration.
This filter can be used to create custom validation rules on user registration. This fires when the form is submitted but before user information is saved to the database.
When used with other hooks, this filter can be used to create custom registration processes.
The form will not create a new user if any errors are returned. Notice: The function must return the variable $errors in any case (even when there is no error in your logic), otherwise the function may cause this problem:
Fatal error: Call to a member function get_error_code() on a non-object.