Revisar los conflictos de versión en las dependencias: "symfony/symfony": "2.7.1" => "symfony/symfony": "2.7.46" "doctrine/doctrine-fixtures-bundle": "2.4.*" => "doctrine/doctrine-fixtures-bundle": "~2.4" "sonata-project/intl-bundle": "2.1.*" => "sonata-project/intl-bundle": "~2.3"