Essaie avec SF4.

composer.json

@@ -27,14 +27,14 @@
         "ext-json": "*",
         "doctrine/doctrine-bundle": "^1.6",
         "doctrine/orm": "^2.5",
-        "symfony/config": "^3.0",
-        "symfony/console": "^3.0",
-        "symfony/dependency-injection": "^3.0",
-        "symfony/filesystem": "^3.0",
-        "symfony/finder": "^3.0",
-        "symfony/framework-bundle": "^3.0",
-        "symfony/http-kernel": "^3.0",
-        "symfony/security": "^3.0"
+        "symfony/config": "^3.0 | ^4.0",
+        "symfony/console": "^3.0 | ^4.0",
+        "symfony/dependency-injection": "^3.0 | ^4.0",
+        "symfony/filesystem": "^3.0 | ^4.0",
+        "symfony/finder": "^3.0 | ^4.0",
+        "symfony/framework-bundle": "^3.0 | ^4.0",
+        "symfony/http-kernel": "^3.0 | ^4.0",
+        "symfony/security": "^3.0 | ^4.0"
     },
     "bin": ["bin/plantuml.jar"],
     "config": {