### Description

The `sendRequest` method is asynchronous and notifies a 
`TransportResponseHandler` when it completes the excecution
(successfully or unsuccessfully). 

When opening the connection we only catch `NodeNotConnectedException`
( https://github.com/elastic/elasticsearch/blob/main/server/src/main/java/org/elasticsearch/transport/TransportService.java#L719 ) which is currently fine as no implementations
throw other type of exception however, it'd be best to catch `Exception` here
so the `handler` gets notified of potential exceptions (as opposed to the caller
having to `try/catch` the call to `sendRequest`)
test/framework/src/main/java/org/elasticsearch/transport/AbstractSimpleTransportTestCase.java
}
                    }
                }
                @Override
                public void onAfter() {
                    done.countDown();
                }
            });
        }
        go.await();
        for (int i = 0; i <= 10; i++) {
            if (i % 3 == 0) {
                
                serviceB.close();
                MockTransportService newService = buildService("TS_B_" + i, version1, Settings.EMPTY);
                newService.registerRequestHandler("internal:test", ThreadPool.Names.SAME, TestRequest::new, ignoringRequestHandler);
                serviceB = newService;
                nodeB = newService.getLocalDiscoNode();
                connectToNode(serviceB, nodeA);
                connectToNode(serviceA, nodeB);
            } else if (serviceA.nodeConnected(nodeB)) {
                serviceA.disconnectFromNode(nodeB);
            } else {
                connectToNode(serviceA, nodeB);
            }
        }
        done.await();
        assertThat("found non connection errors while sending", sendingErrors, empty());
        assertThat("found non connection errors while responding", responseErrors, empty());
    }