fixed Doctrine migrations default configuration

doctrine/doctrine-migrations-bundle/1.2/config/packages/doctrine_migrations.yaml

@@ -1,2 +1,5 @@
 doctrine_migrations:
     dir_name: '%kernel.project_dir%/src/Migrations'
+    # namespace is arbitrary but should be different from App\Migrations
+    # as migrations classes should NOT be autoloaded
+    namespace: DoctrineMigrations

symfony/framework-bundle/3.3/config/services.yaml

@@ -19,7 +19,7 @@ services:
         resource: '../src/*'
         # you can exclude directories or files
         # but if a service is unused, it's removed anyway
-        exclude: '../src/{Entity,Repository,Tests}'
+        exclude: '../src/{Entity,Migrations,Repository,Tests}'
 
     # controllers are imported separately to make sure they're public
     # and have a tag that allows actions to type-hint services