minor symfony#19158 [Console] LockableTrait: change visibility to private (xabbuh)

This PR was merged into the 3.2-dev branch.

Discussion
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[Console] LockableTrait: change visibility to private

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | symfony#18471 (comment)
| License       | MIT
| Doc PR        |

Without this change we force users to expose unnecessary extension points they may not want to provide.

Commits
-------

eaa3bb0 LockableTrait: change visibility to private

Author: fabpot

src/Symfony/Component/Console/Command/LockableTrait.php

@@ -22,14 +22,14 @@
  */
 trait LockableTrait
 {
-    protected $lockHandler;
+    private $lockHandler;
 
     /**
      * Locks a command.
      *
      * @return bool
      */
-    protected function lock($name = null, $blocking = false)
+    private function lock($name = null, $blocking = false)
     {
         if (!class_exists(LockHandler::class)) {
             throw new RuntimeException('To enable the locking feature you must install the symfony/filesystem component.');
@@ -53,7 +53,7 @@ protected function lock($name = null, $blocking = false)
     /**
      * Releases the command lock if there is one.
      */
-    protected function release()
+    private function release()
     {
         if ($this->lockHandler) {
             $this->lockHandler->release();