Comment out broken test (return type does not exist)

core/helper_test.go

@@ -5,7 +5,7 @@ import (
 	"fmt"
 
 	"github.com/ethereum/go-ethereum/core/types"
-	"github.com/ethereum/go-ethereum/crypto"
+	// "github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/ethutil"
 	"github.com/ethereum/go-ethereum/event"
@@ -53,9 +53,10 @@ func (tm *TestManager) TxPool() *TxPool {
 func (tm *TestManager) EventMux() *event.TypeMux {
 	return tm.eventMux
 }
-func (tm *TestManager) KeyManager() *crypto.KeyManager {
-	return nil
-}
+
+// func (tm *TestManager) KeyManager() *crypto.KeyManager {
+// 	return nil
+// }
 
 func (tm *TestManager) Db() ethutil.Database {
 	return tm.db