Fix test failed

Author: shenh062326

core/src/main/scala/org/apache/spark/HeartbeatReceiver.scala

@@ -84,7 +84,7 @@ private[spark] class HeartbeatReceiver(sc: SparkContext, scheduler: TaskSchedule
     for ((executorId, lastSeenMs) <- executorLastSeen) {
       if (lastSeenMs < minSeenTime) {
         logWarning("Removing Executor " + executorId + " with no recent heartbeats: "
-            +(now - lastSeenMs) + "ms exceeds " + slaveTimeout + "ms")
+            + (now - lastSeenMs) + "ms exceeds " + slaveTimeout + "ms")
         scheduler.executorLost(executorId, SlaveLost)
         sc.killExecutor(executorId)
         executorLastSeen.remove(executorId)