Fix file_get_content exception when installing symfony 4.3-dev

Author: jlslew

src/Configurator/AbstractConfigurator.php

@@ -78,7 +78,7 @@ protected function updateData(string $file, string $data): bool
         $pieces = explode("\n", trim($data));
         $startMark = trim(reset($pieces));
         $endMark = trim(end($pieces));
-        $contents = file_get_contents($file);
+        $contents = @file_get_contents($file);
 
         if (false === strpos($contents, $startMark) || false === strpos($contents, $endMark)) {
             return false;