eth: gracefully error if database cannot be opened

eth/backend.go

@@ -200,10 +200,13 @@ func makeExtraData(extra []byte) []byte {
 // CreateDB creates the chain database.
 func CreateDB(ctx *node.ServiceContext, config *Config, name string) (ethdb.Database, error) {
 	db, err := ctx.OpenDatabase(name, config.DatabaseCache, config.DatabaseHandles)
+	if err != nil {
+		return nil, err
+	}
 	if db, ok := db.(*ethdb.LDBDatabase); ok {
 		db.Meter("eth/db/chaindata/")
 	}
-	return db, err
+	return db, nil
 }
 
 // CreateConsensusEngine creates the required type of consensus engine instance for an Ethereum service