Test: Skip assertion on windows

Windows doesn't provide consistent exception messages when it can't
connect so skip the exception message assertion on windows.

Closes #31457

Author: nik9000

client/rest/src/test/java/org/elasticsearch/client/RestClientMultipleHostsIntegTests.java

@@ -42,9 +42,7 @@
 import static org.elasticsearch.client.RestClientTestUtil.getAllStatusCodes;
 import static org.elasticsearch.client.RestClientTestUtil.randomErrorNoRetryStatusCode;
 import static org.elasticsearch.client.RestClientTestUtil.randomOkStatusCode;
-import static org.hamcrest.Matchers.startsWith;
 import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertThat;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
 
@@ -216,8 +214,10 @@ public void testNodeSelector() throws IOException {
                     restClient.performRequest(request);
                     fail("expected to fail to connect");
                 } catch (ConnectException e) {
-                    // This is different in windows and linux but this matches both.
-                    assertThat(e.getMessage(), startsWith("Connection refused"));
+                    // Windows isn't consistent here. Sometimes the message is even null!
+                    if (false == System.getProperty("os.name").startsWith("Windows")) {
+                        assertEquals("Connection refused", e.getMessage());
+                    }
                 }
             } else {
                 Response response = restClient.performRequest(request);