Change assertion so it works in every locale (elastic#138984)

Author: mamazzol

muted-tests.yml

@@ -463,9 +463,6 @@ tests:
 - class: org.elasticsearch.common.settings.ScopedSettingsTests
   method: testValidateArchivedSetting
   issue: https://github.com/elastic/elasticsearch/issues/138895
-- class: org.elasticsearch.test.rest.yaml.ESClientYamlSuiteTestCaseMultipleFailuresIT
-  method: test {p0=/20_multiple_failures/Test with multiple failures}
-  issue: https://github.com/elastic/elasticsearch/issues/138896
 - class: org.elasticsearch.test.rest.yaml.CcsCommonYamlTestSuiteIT
   method: test {p0=search/610_function_score/formulating a function score query with a negative number returns bad request}
   issue: https://github.com/elastic/elasticsearch/issues/138908

test/yaml-rest-runner/src/main/java/org/elasticsearch/test/rest/yaml/ESClientYamlSuiteTestCase.java

@@ -587,7 +587,7 @@ public void verify() throws AssertionError {
             try {
                 super.verify();
             } catch (Throwable e) {
-                throw new AssertionError(e.getMessage());
+                throw new AssertionError(e);
             }
         }
     }

test/yaml-rest-runner/src/yamlRestTest/java/org/elasticsearch/test/rest/yaml/ESClientYamlSuiteTestCaseMultipleFailuresIT.java

@@ -14,11 +14,16 @@
 import org.elasticsearch.test.cluster.ElasticsearchCluster;
 import org.elasticsearch.test.junit.annotations.TestLogging;
 import org.junit.ClassRule;
+import org.junit.runners.model.MultipleFailureException;
 
 import java.io.IOException;
 import java.util.Collections;
 
+import static org.hamcrest.Matchers.containsInAnyOrder;
 import static org.hamcrest.Matchers.containsString;
+import static org.hamcrest.Matchers.hasSize;
+import static org.hamcrest.Matchers.hasToString;
+import static org.hamcrest.Matchers.instanceOf;
 
 public class ESClientYamlSuiteTestCaseMultipleFailuresIT extends ESClientYamlSuiteTestCase {
 
@@ -48,14 +53,17 @@ public void test() throws IOException {
         try {
             super.test();
         } catch (AssertionError error) {
-            String message = error.getMessage();
-            assertThat("Error message should start with failure count", message, containsString("There were 3 errors"));
-            assertThat("Error message should contain first failure", message, containsString("wrong_value1"));
-            assertThat("Error message should contain second failure", message, containsString("wrong_value2"));
-            assertThat("Error message should contain third failure", message, containsString("wrong_value3"));
-            assertThat("Error message should contain actual value1", message, containsString("value1"));
-            assertThat("Error message should contain actual value2", message, containsString("value2"));
-            assertThat("Error message should contain actual value3", message, containsString("value3"));
+            assertThat(error.getCause(), instanceOf(MultipleFailureException.class));
+            MultipleFailureException cause = (MultipleFailureException) error.getCause();
+            assertThat(cause.getFailures(), hasSize(3));
+            assertThat(
+                cause.getFailures(),
+                containsInAnyOrder(
+                    hasToString(containsString("wrong_value1")),
+                    hasToString(containsString("wrong_value2")),
+                    hasToString(containsString("wrong_value3"))
+                )
+            );
         }
     }