Both the ItemTreePanel Status bar and the Final Grade Submission (FGS) tool dialog use the REST call '/AppConstants.GRADES_VERIFICATION_FRAGMENT/{guid}/{gid}' to get the gradebook setup status

All the data these two processes need is already available in the itemtreepanel (client) .... errors are styled with css().gbCellError, etc. ....

Reasons to refactor:
1) avoid a service call
2) the service method the that the REST call is mapped to returns the number of learners and whether there are ungraded items, and neither of these datum is used in FSG or the Status Bar.
3) the service method the that the REST call is mapped to misses catching <> 100% category total if some cats have fractional contributions (eg, 44.3%)

We may need to keep the service method around for other purposes, particularly if those purposes include data in #2.... if so we would need to fix #3
In any case, #1 alone seems sufficient justification for a refactor.

coding related to #2 or #3 should probably be in another (service component) jira