Phpmd error msg fix

Author: mmarynich

src/PhpGitHooks/Module/PhpMd/Infrastructure/Tool/PhpMdToolProcessor.php

@@ -57,8 +57,20 @@ private function execute($file, $options)
      *
      * @return null|string
      */
+
+    /**
+     * @param Process $process
+     *
+     * @return null|string
+     *
+     * @throws \Symfony\Component\Process\Exception\LogicException
+     */
     private function setError(Process $process)
     {
-        return false === $process->isSuccessful() ? $process->getErrorOutput() : null;
+        if (false === $process->isSuccessful()) {
+            return $process->getErrorOutput() ?: $process->getOutput();
+        }
+
+        return null;
     }
 }