replaced DB_URL by DATABASE_URL

doctrine/doctrine-bundle/1.6/etc/packages/doctrine.yaml

@@ -1,6 +1,6 @@
 doctrine:
     dbal:
-        url: "%env(DB_URL)%"
+        url: "%env(DATABASE_URL)%"
     orm:
         auto_generate_proxy_classes: "%kernel.debug%"
         naming_strategy: doctrine.orm.naming_strategy.underscore

doctrine/doctrine-bundle/1.6/manifest.json

@@ -8,7 +8,7 @@
     },
     "env": {
         "#1": "For a sqlite database, use: \"sqlite:///%kernel.project_dir%/var/data.db\"",
-        "DB_URL": "mysql://root@127.0.0.1:3306/symfony?charset=utf8mb4"
+        "DATABASE_URL": "mysql://root@127.0.0.1:3306/symfony?charset=utf8mb4"
     },
     "aliases": ["doctrine", "orm"]
 }