Fatal error with Symfony 3.4 and symfony/phpunit-bridge about phpunit-speedtrap HOT 4 OPEN

{
    "name": "luca/base-project",
    "license": "proprietary",
    "type": "project",
    "autoload": {
        "psr-4": {
            "AppBundle\\": "src/AppBundle",
            "Application\\Sonata\\UserBundle\\": "src/Application/Sonata/UserBundle",
            "Application\\Sonata\\MediaBundle\\": "src/Application/Sonata/MediaBundle"
        },
        "classmap": [
            "app/AppKernel.php",
            "app/AppCache.php"
        ]
    },
    "autoload-dev": {
        "psr-4": {
            "Tests\\": "tests/"
        },
        "files": [
            "vendor/symfony/symfony/src/Symfony/Component/VarDumper/Resources/functions/dump.php"
        ]
    },
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        "incenteev/composer-parameter-handler": "^2.0",
        "jms/serializer-bundle": "^2.4",
        "leafo/scssphp": "^0.7.7",
        "patchwork/jsqueeze": "^2.0",
        "php-translation/symfony-bundle": "^0.8.1",
        "sensio/distribution-bundle": "^5.0.19",
        "sensio/framework-extra-bundle": "^5.0.0",
        "sonata-project/admin-bundle": "^3.35",
        "sonata-project/core-bundle": "dev-use-new-classes as 3.15.1",
        "sonata-project/doctrine-orm-admin-bundle": "^3.6",
        "sonata-project/easy-extends-bundle": "^2.5",
        "sonata-project/media-bundle": "^3.13",
        "sonata-project/translation-bundle": "^2.3",
        "sonata-project/user-bundle": "^4.1",
        "stof/doctrine-extensions-bundle": "^1.3",
        "symfony/assetic-bundle": "^2.8",
        "symfony/monolog-bundle": "^3.1.0",
        "symfony/polyfill-apcu": "^1.0",
        "symfony/swiftmailer-bundle": "^2.6.4",
        "symfony/symfony": "3.4.*",
        "twig/twig": "^1.0||^2.0"
    },
    "require-dev": {
        "doctrine/doctrine-fixtures-bundle": "^3.0",
        "liip/functional-test-bundle": "~2.0@alpha",
        "phpstan/phpstan": "^0.9.2",
        "sensio/generator-bundle": "^3.0",
        "symfony/phpunit-bridge": "^4.1"
    },
    "scripts": {
        "symfony-scripts": [
            "Incenteev\\ParameterHandler\\ScriptHandler::buildParameters",
            "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::buildBootstrap",
            "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::clearCache",
            "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::installAssets",
            "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::installRequirementsFile",
            "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::prepareDeploymentTarget"
        ],
        "post-install-cmd": [
            "@symfony-scripts"
        ],
        "post-update-cmd": [
            "@symfony-scripts"
        ]
    },
    "config": {
        "sort-packages": true
    },
    "extra": {
        "symfony-app-dir": "app",
        "symfony-bin-dir": "bin",
        "symfony-var-dir": "var",
        "symfony-web-dir": "web",
        "symfony-tests-dir": "tests",
        "symfony-assets-install": "relative",
        "incenteev-parameters": {
            "file": "app/config/parameters.yml"
        },
        "branch-alias": null
    }
}