Improve error message in 151-OpenFileLimit.

Bug: 77641050
Test: ./art/test/testrunner/testrunner.py -b --host --jit --32 -t 151-OpenFileLimit
Change-Id: Icb75fa08d3a61ce93dcadba43e4f1c558e131df4
diff --git a/test/151-OpenFileLimit/src/Main.java b/test/151-OpenFileLimit/src/Main.java
index de5890c..9b16090 100644
--- a/test/151-OpenFileLimit/src/Main.java
+++ b/test/151-OpenFileLimit/src/Main.java
@@ -38,7 +38,8 @@
             if (e.getMessage().contains("Too many open files")) {
                 System.out.println("Message includes \"Too many open files\"");
             } else {
-                System.out.println(e.getMessage());
+                System.out.println("Unexpected exception:");
+                e.printStackTrace();
             }
         }