(Hi Davo).
I was upgrading my moodle from version 2.9.3 to 3.0 and encountered a problem with the "Checklist" block plugin. It doesn't work, and it prevents my moodle upgrade from completing. The solution is to remove this plugin. The "Checklist" mod plugin works.
The two error messages that I get are shown below.
Has anyone else had success using "Checklist" block with Moodle 3.0?