We call DiscoverTopology as a last step if checkMetadataConsistency fails with CommandNotFound as part of the background hook. Then, we assert that we are running in a sharded cluster to prevent developers from adding this background hook in inappropriate contexts, such as replica set suites.

However, we do not throw the last exception — we simply log it. We should ignore all errors coming from DiscoverTopology, but still perform the assertion to ensure the hook is not run in non-sharded clusters.