add quotes in error message

Author: inlined

firebase-database/src/test/java/com/google/firebase/database/util/ComparatorTester.java

@@ -166,7 +166,7 @@ private final void doTestEqualsCompatibility() {
           for (Object other : otherGroup) {
             // Testing equals() for compatibility with compare()/compareTo(),
             // add a call to doNotRequireEqualsCompatibility() if this is not required
-            assertWithMessage("%s.equals(%s)", reference, other)
+            assertWithMessage("\"%s\".equals(\"%s\")", reference, other)
                 .that(reference.equals(other))
                 .isEqualTo(compare(reference, other) == 0);
           }