Using Command output as message which actually provides more informat…

…ion for debugging than just the path

dev/tests/static/testsuite/Magento/Test/Integrity/ComposerTest.php

@@ -103,7 +103,7 @@ private function validateComposerJsonFile($path)
         try {
             $app->runComposerCommand(['command' => 'validate'], $path);
         } catch (\RuntimeException $exception) {
-            $this->fail("Failed validation of {$path}");
+            $this->fail($exception->getMessage());
         }
     }