improve message when workflows are missing

src/Symfony/Bundle/FrameworkBundle/DependencyInjection/FrameworkExtension.php

@@ -397,6 +397,10 @@ class FrameworkExtension extends Extension
             return;
         }
 
+        if (!class_exists(Workflow\Workflow::class)) {
+            throw new LogicException('Workflow support cannot be enabled as the Workflow component is not installed.');
+        }
+
         $loader->load('workflow.xml');
 
         $registryDefinition = $container->getDefinition('workflow.registry');

src/Symfony/Bundle/FrameworkBundle/composer.json

@@ -50,6 +50,7 @@
         "symfony/translation": "~3.2",
         "symfony/templating": "~2.8|~3.0",
         "symfony/validator": "~3.2",
+        "symfony/workflow": "~3.2",
         "symfony/yaml": "~3.2",
         "symfony/property-info": "~3.1",
         "doctrine/annotations": "~1.0",