Address PR comments

core/blockchain.go

@@ -174,7 +174,6 @@ func NewBlockChain(db ethdb.Database, cacheConfig *CacheConfig, chainConfig *par
 	bc.SetProcessor(NewStateProcessor(chainConfig, bc, engine))
 
 	var err error
-
 	bc.hc, err = NewHeaderChain(db, chainConfig, engine, bc.getProcInterrupt)
 	if err != nil {
 		return nil, err
@@ -1188,7 +1187,6 @@ func (bc *BlockChain) insertChain(chain types.Blocks) (int, []interface{}, []*ty
 			parent = chain[i-1]
 		}
 		state, err := state.New(parent.Root(), bc.stateCache)
-
 		if err != nil {
 			return i, events, coalescedLogs, err
 		}

statediff/extractor/extractor.go

@@ -34,11 +34,11 @@ type extractor struct {
 	Publisher publisher.Publisher // Interface for publishing state diff objects to a datastore (e.g. IPFS)
 }
 
-func NewExtractor(builder builder.Builder, publisher publisher.Publisher) (*extractor, error) {
+func NewExtractor(builder builder.Builder, publisher publisher.Publisher) *extractor {
 	return &extractor{
 		Builder:   builder,
 		Publisher: publisher,
-	}, nil
+	}
 }
 
 func (e *extractor) ExtractStateDiff(parent, current types.Block) (string, error) {

statediff/extractor/extractor_test.go

@@ -23,7 +23,7 @@ var err error
 func TestExtractor(t *testing.T) {
 	publisher = mocks.Publisher{}
 	builder = mocks.Builder{}
-	extractor, err = e.NewExtractor(&builder, &publisher)
+	extractor = e.NewExtractor(&builder, &publisher)
 	if err != nil {
 		t.Error(err)
 	}

statediff/service/service.go

@@ -31,10 +31,10 @@ func NewStateDiffService(db ethdb.Database, blockChain *core.BlockChain, config
 	builder := b.NewBuilder(db)
 	publisher, err := p.NewPublisher(config)
 	if err != nil {
-		return nil, nil
+		return nil, err
 	}
 
-	extractor, _ := e.NewExtractor(builder, publisher)
+	extractor := e.NewExtractor(builder, publisher)
 	return &StateDiffService{
 		BlockChain: blockChain,
 		Extractor:  extractor,