Added require to Utils#startServiceOnPort

Author: sarutak

core/src/main/scala/org/apache/spark/util/Utils.scala

@@ -1879,10 +1879,9 @@ private[spark] object Utils extends Logging {
       conf: SparkConf,
       serviceName: String = ""): (T, Int) = {
 
-    if (startPort != 0 && (startPort < 1024 || startPort >= 65536)) {
-      throw new IllegalArgumentException("startPort should be between " +
+    require(startPort == 0 || 1024 <= startPort && startPort < 65536,
+      "startPort should be between " +
         "1024(including) and 65536(excluding) or 0(for a random free port).")
-    }
 
     val serviceString = if (serviceName.isEmpty) "" else s" '$serviceName'"
     val maxRetries = portMaxRetries(conf)

external/flume/src/test/scala/org/apache/spark/streaming/flume/FlumeStreamSuite.scala

@@ -20,14 +20,13 @@ package org.apache.spark.streaming.flume
 import java.net.{InetSocketAddress, ServerSocket}
 import java.nio.ByteBuffer
 
-import org.apache.commons.lang3.RandomUtils
-
 import scala.collection.JavaConversions._
 import scala.collection.mutable.{ArrayBuffer, SynchronizedBuffer}
 import scala.concurrent.duration._
 import scala.language.postfixOps
 
 import com.google.common.base.Charsets
+import org.apache.commons.lang3.RandomUtils
 import org.apache.avro.ipc.NettyTransceiver
 import org.apache.avro.ipc.specific.SpecificRequestor
 import org.apache.flume.source.avro