Currently, any failed request to the source Wiki will result in the target Wikibase entering an error state. One situation that needs to be handled is when saving an edit is attempted and fails because accessing the source wiki is impossible.
If looking up the property data type fails while adding/editing a statement, then we should display an error message when save is selected: "Your save failed due to a failed request to the federation source Wiki.."
Given I am adding or editing a statement with federated properties enabled
And the lookup of the property data type fails due to a failed call to the source Wiki
When I select save
Then an error message is displayed that indicates my save failed due to failed call to source Wiki
Note: this needs to be made testable in the test system for product verification to take place!