[SPARK-20260][MLLIB] String interpolation required for error message

## What changes were proposed in this pull request?
This error message doesn't get properly formatted because of a missing `s`.  Currently the error looks like:

```
Caused by: java.lang.IllegalArgumentException: requirement failed: indices should be one-based and in ascending order; found current=$current, previous=$previous; line="$line"
```
(note the literal `$current` instead of the interpolated value)

Please review http://spark.apache.org/contributing.html before opening a pull request.

Author: Vijay Ramesh <vramesh@demandbase.com>

Closes #17572 from vijaykramesh/master.

4 files changed, 5 insertions, 5 deletions

diff --git a/mllib/src/main/scala/org/apache/spark/mllib/clustering/PowerIterationClustering.scala b/mllib/src/main/scala/org/apache/spark/mllib/clustering/PowerIterationClustering.scala
index 4d3e265455..b2437b845f 100644
--- a/mllib/src/main/scala/org/apache/spark/mllib/clustering/PowerIterationClustering.scala
+++ b/mllib/src/main/scala/org/apache/spark/mllib/clustering/PowerIterationClustering.scala
@@ -259,7 +259,7 @@ object PowerIterationClustering extends Logging {
         val j = ctx.dstId
         val s = ctx.attr
         if (s < 0.0) {
-          throw new SparkException("Similarity must be nonnegative but found s($i, $j) = $s.")
+          throw new SparkException(s"Similarity must be nonnegative but found s($i, $j) = $s.")
         }
         if (s > 0.0) {
           ctx.sendToSrc(s)
@@ -283,7 +283,7 @@ object PowerIterationClustering extends Logging {
     : Graph[Double, Double] = {
     val edges = similarities.flatMap { case (i, j, s) =>
       if (s < 0.0) {
-        throw new SparkException("Similarity must be nonnegative but found s($i, $j) = $s.")
+        throw new SparkException(s"Similarity must be nonnegative but found s($i, $j) = $s.")
       }
       if (i != j) {
         Seq(Edge(i, j, s), Edge(j, i, s))
diff --git a/mllib/src/main/scala/org/apache/spark/mllib/tree/model/DecisionTreeModel.scala b/mllib/src/main/scala/org/apache/spark/mllib/tree/model/DecisionTreeModel.scala
index a1562384b0..27618e122a 100644
--- a/mllib/src/main/scala/org/apache/spark/mllib/tree/model/DecisionTreeModel.scala
+++ b/mllib/src/main/scala/org/apache/spark/mllib/tree/model/DecisionTreeModel.scala
@@ -248,7 +248,7 @@ object DecisionTreeModel extends Loader[DecisionTreeModel] with Logging {
       // Build node data into a tree.
       val trees = constructTrees(nodes)
       assert(trees.length == 1,
-        "Decision tree should contain exactly one tree but got ${trees.size} trees.")
+        s"Decision tree should contain exactly one tree but got ${trees.size} trees.")
       val model = new DecisionTreeModel(trees(0), Algo.fromString(algo))
       assert(model.numNodes == numNodes, s"Unable to load DecisionTreeModel data from: $dataPath." +
         s" Expected $numNodes nodes but found ${model.numNodes}")
diff --git a/mllib/src/main/scala/org/apache/spark/mllib/util/MLUtils.scala b/mllib/src/main/scala/org/apache/spark/mllib/util/MLUtils.scala
index 95f904dac5..4fdad05973 100644
--- a/mllib/src/main/scala/org/apache/spark/mllib/util/MLUtils.scala
+++ b/mllib/src/main/scala/org/apache/spark/mllib/util/MLUtils.scala
@@ -119,7 +119,7 @@ object MLUtils extends Logging {
     while (i < indicesLength) {
       val current = indices(i)
       require(current > previous, s"indices should be one-based and in ascending order;"
-        + " found current=$current, previous=$previous; line=\"$line\"")
+        + s""" found current=$current, previous=$previous; line="$line"""")
       previous = current
       i += 1
     }
diff --git a/mllib/src/test/scala/org/apache/spark/mllib/util/TestingUtils.scala b/mllib/src/test/scala/org/apache/spark/mllib/util/TestingUtils.scala
index 39a6bc37d9..d39865a19a 100644
--- a/mllib/src/test/scala/org/apache/spark/mllib/util/TestingUtils.scala
+++ b/mllib/src/test/scala/org/apache/spark/mllib/util/TestingUtils.scala
@@ -207,7 +207,7 @@ object TestingUtils {
       if (r.fun(x, r.y, r.eps)) {
         throw new TestFailedException(
           s"Did not expect \n$x\n and \n${r.y}\n to be within " +
-            "${r.eps}${r.method} for all elements.", 0)
+            s"${r.eps}${r.method} for all elements.", 0)
       }
       true
     }