Custom report items were detected on the report server
Custom report items that were created for previous releases of SQL Server Reporting Services are not compatible with SQL Server 2012 Reporting Services. Upgrade can continue, but reports that use the custom report item will not run as expected. Upgrade Advisor detected custom report items. Upgrade can continue, but you must manually move the custom report item files to the new installation folder after upgrade completes.
Upgrade Advisor detected custom extension settings in the configuration files, indicating that your installation includes one or more custom assemblies for reports.
After upgrade completes, manually move the custom report item files to the new installation folder.