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

Command/LintCommand.php

@@ -202,7 +202,7 @@ private function displayJson(OutputInterface $output, $filesInfo)
             }
         });
 
-        $output->writeln(json_encode($filesInfo, JSON_PRETTY_PRINT));
+        $output->writeln(json_encode($filesInfo, JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES));
 
         return min($errors, 1);
     }