Fail when the forked test harness fails

Fixes #2442/#2722

main/actions/src/main/scala/sbt/ForkTests.scala

@@ -4,6 +4,7 @@
 package sbt
 
 import scala.collection.mutable
+import scala.util.control.NonFatal
 import testing._
 import java.net.ServerSocket
 import java.io._
@@ -73,6 +74,8 @@ private[sbt] object ForkTests {
             os.flush()
 
             new React(is, os, log, opts.testListeners, resultsAcc).react()
+          } catch {
+            case NonFatal(e) => resultsAcc("Forked test harness failed: " + e.getMessage) = SuiteResult.Error
           } finally {
             is.close(); os.close(); socket.close()
           }

notes/0.13.13/fork_test.md

@@ -0,0 +1,8 @@
+### Bug fixes
+
+- Fixes forked test succeeding when the test harness fails. [#2442][2442]/[#2730][2730] by [@eed3si9n][@eed3si9n]/[@dwijnand][@dwijnand}
+
+  [2442]: https://github.com/sbt/sbt/issues/2442
+  [2730]: https://github.com/sbt/sbt/pull/2730
+  [@eed3si9n]: https://github.com/eed3si9n
+  [@dwijnand]: https://github.com/dwijnand