Add Exception class name to message in `NotSerializableExceptionWrapper`

Previously it's possible to get errors like:

```
Caused by: NotSerializableExceptionWrapper[d:\shared_data\afs-issue-1-1\23]
```

Which doesn't tell us what the underlying exception type was that could
not be serialized.

This changes the message to prepend the
`ElasticsearchException.getExceptionName()` of the exception (which is a
underscore case of the class with the leading 'Elasticsearch' removed)

core/src/main/java/org/elasticsearch/common/io/stream/NotSerializableExceptionWrapper.java

@@ -38,7 +38,8 @@ public final class NotSerializableExceptionWrapper extends ElasticsearchExceptio
     private final RestStatus status;
 
     public NotSerializableExceptionWrapper(Throwable other) {
-        super(other.getMessage(), other.getCause());
+        super(ElasticsearchException.getExceptionName(other) +
+                        ": " + other.getMessage(), other.getCause());
         this.name = ElasticsearchException.getExceptionName(other);
         this.status = ExceptionsHelper.status(other);
         setStackTrace(other.getStackTrace());

core/src/test/java/org/elasticsearch/ESExceptionTests.java

@@ -286,12 +286,12 @@ public class ESExceptionTests extends ESTestCase {
     public void testSerializeUnknownException() throws IOException {
         BytesStreamOutput out = new BytesStreamOutput();
         ParsingException ParsingException = new ParsingException(1, 2, "foobar", null);
-        Throwable ex = new Throwable("wtf", ParsingException);
+        Throwable ex = new Throwable("eggplant", ParsingException);
         out.writeThrowable(ex);
 
         StreamInput in = StreamInput.wrap(out.bytes());
         Throwable throwable = in.readThrowable();
-        assertEquals("wtf", throwable.getMessage());
+        assertEquals("throwable: eggplant", throwable.getMessage());
         assertTrue(throwable instanceof ElasticsearchException);
         ParsingException e = (ParsingException)throwable.getCause();
                 assertEquals(ParsingException.getIndex(), e.getIndex());
@@ -329,7 +329,9 @@ public class ESExceptionTests extends ESTestCase {
             StreamInput in = StreamInput.wrap(out.bytes());
             ElasticsearchException e = in.readThrowable();
             assertEquals(e.getMessage(), ex.getMessage());
-            assertEquals(ex.getCause().getClass().getName(), e.getCause().getMessage(), ex.getCause().getMessage());
+            assertTrue("Expected: " + e.getCause().getMessage() + " to contain: " +
+                            ex.getCause().getClass().getName() + " but it didn't",
+                    e.getCause().getMessage().contains(ex.getCause().getMessage()));
             if (ex.getCause().getClass() != Throwable.class) { // throwable is not directly mapped
                 assertEquals(e.getCause().getClass(), ex.getCause().getClass());
             } else {

core/src/test/java/org/elasticsearch/ExceptionSerializationTests.java

@@ -543,9 +543,9 @@ public class ExceptionSerializationTests extends ESTestCase {
 
     public void testNotSerializableExceptionWrapper() throws IOException {
         NotSerializableExceptionWrapper ex = serialize(new NotSerializableExceptionWrapper(new NullPointerException()));
-        assertEquals("{\"type\":\"null_pointer_exception\",\"reason\":null}", toXContent(ex));
+        assertEquals("{\"type\":\"null_pointer_exception\",\"reason\":\"null_pointer_exception: null\"}", toXContent(ex));
         ex = serialize(new NotSerializableExceptionWrapper(new IllegalArgumentException("nono!")));
-        assertEquals("{\"type\":\"illegal_argument_exception\",\"reason\":\"nono!\"}", toXContent(ex));
+        assertEquals("{\"type\":\"illegal_argument_exception\",\"reason\":\"illegal_argument_exception: nono!\"}", toXContent(ex));
 
         Throwable[] unknowns = new Throwable[]{
                 new Exception("foobar"),
@@ -586,7 +586,7 @@ public class ExceptionSerializationTests extends ESTestCase {
         ElasticsearchException serialize = serialize((ElasticsearchException) uhe);
         assertTrue(serialize instanceof NotSerializableExceptionWrapper);
         NotSerializableExceptionWrapper e = (NotSerializableExceptionWrapper) serialize;
-        assertEquals("msg", e.getMessage());
+        assertEquals("unknown_header_exception: msg", e.getMessage());
         assertEquals(2, e.getHeader("foo").size());
         assertEquals("foo", e.getHeader("foo").get(0));
         assertEquals("bar", e.getHeader("foo").get(1));

core/src/test/java/org/elasticsearch/transport/AbstractSimpleTransportTestCase.java

@@ -429,7 +429,7 @@ public abstract class AbstractSimpleTransportTestCase extends ESTestCase {
 
                     @Override
                     public void handleException(TransportException exp) {
-                        assertThat("bad message !!!", equalTo(exp.getCause().getMessage()));
+                        assertThat("runtime_exception: bad message !!!", equalTo(exp.getCause().getMessage()));
                     }
                 });
 
@@ -437,7 +437,7 @@ public abstract class AbstractSimpleTransportTestCase extends ESTestCase {
             res.txGet();
             fail("exception should be thrown");
         } catch (Exception e) {
-            assertThat(e.getCause().getMessage(), equalTo("bad message !!!"));
+            assertThat(e.getCause().getMessage(), equalTo("runtime_exception: bad message !!!"));
         }
 
         serviceA.removeHandler("sayHelloException");