Merge branch '2.8' into 3.2

* 2.8:
  Add missing conflict rules for phpunit

Author: nicolas-grekas

composer.json

@@ -34,6 +34,7 @@
         "symfony/var-dumper": "~3.2"
     },
     "conflict": {
+        "phpunit/phpunit": "<4.8.35|<5.4.3,>=5.0",
         "symfony/doctrine-bridge": "<2.7",
         "symfony/framework-bundle": "<2.7",
         "symfony/twig-bridge": "<2.7"