Fail status more softly unless -vvv is used, refs #11889

src/Composer/Downloader/FileDownloader.php

@@ -524,9 +524,13 @@ class FileDownloader implements DownloaderInterface, ChangeReportInterface
         $this->io = $prevIO;
 
         if ($e !== null) {
+            if ($this->io->isDebug()) {
                 throw $e;
             }
 
+            return 'Failed to detect changes: ['.get_class($e).'] '.$e->getMessage();
+        }
+
         $output = trim($output);
 
         return strlen($output) > 0 ? $output : null;