Dumping file buckets puts the BridgeDB database in an unrecognized state
When we're dumping bridges to files using the
--dump-bridges option, BridgeDB changes the distributor from
pseudo-name in the database. However, when starting BridgeDB normally afterwards, it has no idea to which ring to add this bridge. In particular,
BridgeSplitter.insert() exits in line
ring.insert(bridge) with a traceback.
This problem is related to legacy/trac#2557 (moved).