Merge pull request #1893 from aerskine/0.13

Fixes #1881. Clone SystemProperties defending against ConcurrentModificationException

notes/0.13.8/clone-properties-in-junit-tests-listener.markdown

@@ -0,0 +1,10 @@
+  [@aerskine]: https://github.com/aerskine
+  [1881]: https://github.com/sbt/sbt/issues/1881
+
+### Fixes with compatibility implications
+
+### Improvements
+
+### Bug fixes
+
+- Fixes sporadic ConcurrentModificationException from JUnitXmlTestsListener. [#1881][1881] by [@aerskine][@aerskine]

testing/src/main/scala/sbt/JUnitXmlTestsListener.scala

@@ -2,6 +2,7 @@ package sbt
 
 import java.io.{ IOException, StringWriter, PrintWriter, File }
 import java.net.InetAddress
+import java.util.Hashtable
 
 import scala.collection.mutable.ListBuffer
 import scala.util.DynamicVariable
@@ -27,7 +28,9 @@ class JUnitXmlTestsListener(val outputDir: String) extends TestsListener {
   val properties =
     <properties>
       {
-        val iter = System.getProperties.entrySet.iterator
+        // create a clone, defending against [[ConcurrentModificationException]]
+        val clonedProperties = System.getProperties.clone.asInstanceOf[Hashtable[AnyRef, AnyRef]]
+        val iter = clonedProperties.entrySet.iterator
         val props: ListBuffer[XNode] = new ListBuffer()
         while (iter.hasNext) {
           val next = iter.next