update error message

Author: cloud-fan

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/ScalaReflection.scala

@@ -943,9 +943,9 @@ trait ScalaReflection extends Logging {
    */
   def getParameterTypeNullability(func: AnyRef): Seq[Boolean] = {
     if (!Properties.versionString.contains("2.11")) {
-      logWarning(s"Scala ${Properties.versionString} is not supported so UDF input parameter "
-        + s"type nullability may be inferred incorrectly. To avoid this problem, use the "
-        + s"latest UDF interfaces instead.")
+      logWarning(s"Scala ${Properties.versionString} cannot get type nullability correctly via " +
+        "reflection, thus Spark cannot add proper input null check for UDF. To avoid this " +
+        "problem, use the typed UDF interfaces instead.")
     }
     val methods = func.getClass.getMethods.filter(m => m.getName == "apply" && !m.isBridge)
     assert(methods.length == 1)