Fix multiFailure format string to avoid nulls

Help when multiple failures are reported

Test: presubmit
Bug: 263402834
Change-Id: Ifa8caddb63085697655cc62a429ebe1aa1b8efe2

javatests/.classpath

diff --git a/javatests/.classpath b/javatests/.classpath
index 636568a..4a0a046 100644
--- a/javatests/.classpath
+++ b/javatests/.classpath
@@ -28,7 +28,6 @@
 	<classpathentry kind="var" path="TRADEFED_ROOT/out/soong/.intermediates/tools/tradefederation/core/tradefed-protos/linux_glibc_common/combined/tradefed-protos.jar"/>
 	<classpathentry kind="var" path="TRADEFED_ROOT/prebuilts/tools/common/google-api-services-storage/1.24.1/google-api-services-storage-v1-rev155-1.24.1.jar"/>
 	<classpathentry kind="var" path="TRADEFED_ROOT/out/soong/.intermediates/external/perfetto/perfetto_metrics-full/linux_glibc_common/combined/perfetto_metrics-full.jar"/>
-	<classpathentry kind="var" path="TRADEFED_ROOT/prebuilts/tools/common/m2/repository/org/mockito/mockito-all/1.9.5/mockito-all-1.9.5.jar"/>
 	<classpathentry kind="var" path="TRADEFED_ROOT/out/soong/.intermediates/external/grpc-grpc-java/grpc-java/linux_glibc_common/combined/grpc-java.jar"/>
 	<classpathentry kind="var" path="TRADEFED_ROOT/out/soong/.intermediates/external/grpc-grpc-java/testing/grpc-java-testing/linux_glibc_common/javac/grpc-java-testing.jar"/>
 	<classpathentry kind="var" path="TRADEFED_ROOT/out/soong/.intermediates/external/protobuf/libprotobuf-java-util-full/linux_glibc_common/combined/libprotobuf-java-util-full.jar"/>

javatests/com/android/tradefed/result/MultiFailureDescriptionTest.java

diff --git a/javatests/com/android/tradefed/result/MultiFailureDescriptionTest.java b/javatests/com/android/tradefed/result/MultiFailureDescriptionTest.java
index e124fea..f7e22c4 100644
--- a/javatests/com/android/tradefed/result/MultiFailureDescriptionTest.java
+++ b/javatests/com/android/tradefed/result/MultiFailureDescriptionTest.java
@@ -49,4 +49,15 @@
                 "There were 2 failures:\n  error message 1\n  error message 2",
                 mMultiFailureDesc.toString());
     }
+
+    @Test
+    public void testFormat() {
+        FailureDescription failure1 = FailureDescription.create("error message 1");
+        FailureDescription failure2 = FailureDescription.create("error message 2");
+        MultiFailureDescription nested = new MultiFailureDescription(failure2);
+        mMultiFailureDesc = new MultiFailureDescription(failure1, nested);
+        assertEquals(
+                "There were 2 failures:\n  error message 1\n  error message 2",
+                mMultiFailureDesc.getFormattedErrorMessage());
+    }
 }

test_result_interfaces/com/android/tradefed/result/FailureDescription.java

diff --git a/test_result_interfaces/com/android/tradefed/result/FailureDescription.java b/test_result_interfaces/com/android/tradefed/result/FailureDescription.java
index 94017a1..bb32a3f 100644
--- a/test_result_interfaces/com/android/tradefed/result/FailureDescription.java
+++ b/test_result_interfaces/com/android/tradefed/result/FailureDescription.java
@@ -176,7 +176,7 @@
             s.append(mErrorId.status());
             s.append("] ");
         }
-        s.append(mErrorMessage);
+        s.append(this.toString());
         return s.toString();
     }