Log test worker failures for CI diagnosis

app/build.gradle

@@ -185,6 +185,15 @@ android {
         unitTests.returnDefaultValues = true
         // Robolectric tests start activities whose text is now all string resources.
         unitTests.includeAndroidResources = true
+        // Temporary diagnostics for the test worker's unexplained exit 2.
+        unitTests.all {
+            systemProperty 'robolectric.logging', 'stdout'
+            testLogging {
+                events 'started', 'failed'
+                exceptionFormat 'full'
+                showStandardStreams = true
+            }
+        }
     }
 
     compileOptions {