Merge branch '3.1'

* 3.1:
  added a comment about a workaround
  [Finder] no PHP warning on empty directory iteration
  [HttpKernel] Fixed the nullable support for php 7.1 and below
  fixed CS
  [Form] Fix typo in doc comment
  Fix version constraint
  [Config] Handle open_basedir restrictions in FileLocator
  Fixed bad merge
  [DoctrineBridge][PropertyInfo] Treat Doctrine decimal type as string
  [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
  [FrameworkBundle] Remove cache clearer default value in config
  Consider the umask setting when dumping a file.
  Fixed the nullable support for php 7.1 and below
  Make ReflectionExtractor compatible with ReflectionType changes in PHP 7.1

Author: fabpot

Iterator/RecursiveDirectoryIterator.php

@@ -137,6 +137,11 @@ public function isRewindable()
             return $this->rewindable;
         }
 
+        // workaround for an HHVM bug, should be removed when https://github.com/facebook/hhvm/issues/7281 is fixed
+        if ('' === $this->getPath()) {
+            return $this->rewindable = false;
+        }
+
         if (false !== $stream = @opendir($this->getPath())) {
             $infos = stream_get_meta_data($stream);
             closedir($stream);