SPARK-2482: Resolve sbt warnings during build

At the same time, import the `scala.language.postfixOps` and ` org.scalatest.time.SpanSugar._` cause `scala.language.postfixOps` doesn't work

Author: witgo <[email protected]>

Closes #1330 from witgo/sbt_warnings3 and squashes the following commits:

179ba61 [witgo] Resolve sbt warnings during build

Author: witgo

bagel/src/test/scala/org/apache/spark/bagel/BagelSuite.scala

@@ -24,8 +24,6 @@ import org.scalatest.time.SpanSugar._
 import org.apache.spark._
 import org.apache.spark.storage.StorageLevel
 
-import scala.language.postfixOps
-
 class TestVertex(val active: Boolean, val age: Int) extends Vertex with Serializable
 class TestMessage(val targetId: String) extends Message[String] with Serializable
 

core/src/test/scala/org/apache/spark/ContextCleanerSuite.scala

@@ -21,7 +21,6 @@ import java.lang.ref.WeakReference
 
 import scala.collection.mutable.{HashSet, SynchronizedSet}
 import scala.language.existentials
-import scala.language.postfixOps
 import scala.util.Random
 
 import org.scalatest.{BeforeAndAfter, FunSuite}

core/src/test/scala/org/apache/spark/DriverSuite.scala

@@ -26,8 +26,6 @@ import org.scalatest.time.SpanSugar._
 
 import org.apache.spark.util.Utils
 
-import scala.language.postfixOps
-
 class DriverSuite extends FunSuite with Timeouts {
 
   test("driver should exit after finishing") {

core/src/test/scala/org/apache/spark/rdd/AsyncRDDActionsSuite.scala

@@ -22,7 +22,6 @@ import java.util.concurrent.Semaphore
 import scala.concurrent.{Await, TimeoutException}
 import scala.concurrent.duration.Duration
 import scala.concurrent.ExecutionContext.Implicits.global
-import scala.language.postfixOps
 
 import org.scalatest.{BeforeAndAfterAll, FunSuite}
 import org.scalatest.concurrent.Timeouts

core/src/test/scala/org/apache/spark/ui/UISuite.scala

@@ -21,7 +21,6 @@ import java.net.ServerSocket
 import javax.servlet.http.HttpServletRequest
 
 import scala.io.Source
-import scala.language.postfixOps
 import scala.util.{Failure, Success, Try}
 
 import org.eclipse.jetty.server.Server

pom.xml

@@ -839,7 +839,6 @@
               <arg>-unchecked</arg>
               <arg>-deprecation</arg>
               <arg>-feature</arg>
-              <arg>-language:postfixOps</arg>
             </args>
             <jvmArgs>
               <jvmArg>-Xms1024m</jvmArg>

repl/src/main/scala/org/apache/spark/repl/SparkILoop.scala

@@ -15,15 +15,15 @@ import scala.tools.nsc._
 import scala.tools.nsc.backend.JavaPlatform
 import scala.tools.nsc.interpreter._
 
-import scala.tools.nsc.interpreter.{ Results => IR }
-import Predef.{ println => _, _ }
-import java.io.{ BufferedReader, FileReader }
+import scala.tools.nsc.interpreter.{Results => IR}
+import Predef.{println => _, _}
+import java.io.{BufferedReader, FileReader}
 import java.net.URI
 import java.util.concurrent.locks.ReentrantLock
 import scala.sys.process.Process
 import scala.tools.nsc.interpreter.session._
-import scala.util.Properties.{ jdkHome, javaVersion }
-import scala.tools.util.{ Javap }
+import scala.util.Properties.{jdkHome, javaVersion}
+import scala.tools.util.{Javap}
 import scala.annotation.tailrec
 import scala.collection.mutable.ListBuffer
 import scala.concurrent.ops
@@ -33,7 +33,7 @@ import scala.tools.nsc.io.{File, Directory}
 import scala.reflect.NameTransformer._
 import scala.tools.nsc.util.ScalaClassLoader._
 import scala.tools.util._
-import scala.language.{implicitConversions, existentials}
+import scala.language.{implicitConversions, existentials, postfixOps}
 import scala.reflect.{ClassTag, classTag}
 import scala.tools.reflect.StdRuntimeTags._
 

streaming/src/test/scala/org/apache/spark/streaming/NetworkReceiverSuite.scala

@@ -20,7 +20,6 @@ package org.apache.spark.streaming
 import java.nio.ByteBuffer
 
 import scala.collection.mutable.ArrayBuffer
-import scala.language.postfixOps
 
 import org.apache.spark.SparkConf
 import org.apache.spark.storage.{StorageLevel, StreamBlockId}

streaming/src/test/scala/org/apache/spark/streaming/StreamingContextSuite.scala

@@ -29,8 +29,6 @@ import org.scalatest.concurrent.Timeouts
 import org.scalatest.exceptions.TestFailedDueToTimeoutException
 import org.scalatest.time.SpanSugar._
 
-import scala.language.postfixOps
-
 class StreamingContextSuite extends FunSuite with BeforeAndAfter with Timeouts with Logging {
 
   val master = "local[2]"

streaming/src/test/scala/org/apache/spark/streaming/StreamingListenerSuite.scala

@@ -20,7 +20,6 @@ package org.apache.spark.streaming
 import scala.collection.mutable.ArrayBuffer
 import scala.concurrent.Future
 import scala.concurrent.ExecutionContext.Implicits.global
-import scala.language.postfixOps
 
 import org.apache.spark.storage.StorageLevel
 import org.apache.spark.streaming.dstream.DStream