Laravel 项目从 5.4 升级到 5.5 Composer update 报错

我的项目是5.4的，使用 composer update 升级到5.5时报如下错误

这是我的composer.json部分 配置

.
.
.
"require": {
        "php": ">=5.6.4",
        "barryvdh/laravel-debugbar": "~2.4",
        "doctrine/dbal": "~2.4",
        "laravel/framework": "5.5.*",
        "laravel/tinker": "~1.0",
        "predis/predis": "^1.1"
    },
    .
    .
    . 
    "scripts": {
        "post-root-package-install": [
            "php -r \"file_exists('.env') || copy('.env.example', '.env');\""
        ],
        "post-create-project-cmd": [
            "php artisan key:generate"
        ],
        "post-install-cmd": [
            "Illuminate\\Foundation\\ComposerScripts::postInstall",
            "php artisan optimize"
        ],
        "post-update-cmd": [
            "Illuminate\\Foundation\\ComposerScripts::postUpdate",
            "php artisan optimize"
        ],
        "post-autoload-dump":[
            "Illuminate\\Foundation\\ComposerScripts::postAutoloadDump",
            "@php artisan package:discover"
        ]
    },

跪求各位帮忙解答一下，谢谢！