Add comment

Author: Tom Graves

repl/scala-2.11/src/main/scala/org/apache/spark/repl/Main.scala

@@ -35,6 +35,7 @@ object Main extends Logging {
   s.processArguments(List("-Yrepl-class-based",
     "-Yrepl-outdir", s"${outputDir.getAbsolutePath}",
     "-classpath", getAddedJars.mkString(File.pathSeparator)), true)
+  // the creation of SecurityManager has to be lazy so SPARK_YARN_MODE is set if needed
   lazy val classServer = new HttpServer(conf, outputDir, new SecurityManager(conf))
   var sparkContext: SparkContext = _
   var sqlContext: SQLContext = _