Merge branch '2.7' into 2.8

* 2.7:
  [Form] Fix typo in doc comment
  [Config] Handle open_basedir restrictions in FileLocator
  [bugfix] [Console] Set `Input::$interactive` to `false` when command is executed with `--quiet` as verbosity level
  Use JSON_UNESCAPED_SLASHES for lint commands output
  Fixed collapsed ChoiceType options attributes
  Fixed the nullable support for php 7.1 and below

Author: fabpot

FileLocator.php

@@ -57,7 +57,7 @@ public function locate($name, $currentPath = null, $first = true)
         $filepaths = array();
 
         foreach ($paths as $path) {
-            if (file_exists($file = $path.DIRECTORY_SEPARATOR.$name)) {
+            if (@file_exists($file = $path.DIRECTORY_SEPARATOR.$name)) {
                 if (true === $first) {
                     return $file;
                 }