cmocka: Add a newline to subunit error output

Signed-off-by: Jakub Hrozek <jakub.hrozek@posteo.se>
diff --git a/src/cmocka.c b/src/cmocka.c
index 26a268d..068bbcb 100644
--- a/src/cmocka.c
+++ b/src/cmocka.c
@@ -2119,7 +2119,7 @@
         print_message("skip: %s\n", test_name);
         break;
     case PRINTF_TEST_ERROR:
-        print_message("error: %s [ %s ]", test_name, error_message);
+        print_message("error: %s [ %s ]\n", test_name, error_message);
         break;
     }
 }