Add psr/cache on Messenger's dependencies

Author: sroze

composer.json

@@ -21,6 +21,7 @@
     },
     "require-dev": {
         "doctrine/dbal": "~2.4",
+        "psr/cache": "~1.0",
         "symfony/console": "~3.4|~4.0",
         "symfony/dependency-injection": "~3.4.19|^4.1.8",
         "symfony/doctrine-bridge": "~3.4|~4.0",