catch
--- a/core/lib/Drupal/Core/Test/FunctionalTestSetupTrait.php
+++ b/core/lib/Drupal/Core/Test/FunctionalTestSetupTrait.php
    }
    // Copy the testing-specific service overrides in place.
    copy($settings_services_file, $directory . '/services.yml');
+
+    $yaml = new SymfonyYaml();
+    $content = file_get_contents($directory . '/services.yml');
-    $content = file_get_contents($directory . '/services.yml');
+    $yaml = new SymfonyYaml();
+    $content = file_get_contents($settings_services_file);