添加Laravel / Cashier

Question

在我的composer.json文件中添加laravel / cashier后尝试运行composer update时出错了。

以下是错误的屏幕截图。似乎不明白错误是什么。

拜托，我在这里错过了什么？

我的composer.json文件在下面

{
"name": "lufficc/xblog",
"description": "A powerful and responsive blog system powered by laravel.",
"keywords": ["blog", "laravel"],
"license": "MIT",
"type": "project",
"require": {
    "php": ">=5.6.4",
    "laravel/framework": "5.4.*",
    "predis/predis": "^1.1",
    "erusev/parsedown": "^1.6",
    "qiniu/php-sdk": "^7.0",
    "laravel/socialite": "^2.0",
    "mews/purifier": "^2.0",
    "league/html-to-markdown": "^4.3",
    "laravel/tinker": "^1.0",
    "laravel/cashier": "~7.0"
},
"require-dev": {
    "fzaninotto/faker": "~1.4",
    "mockery/mockery": "0.9.*",
    "phpunit/phpunit": "~5.0",
    "symfony/css-selector": "3.1.*",
    "symfony/dom-crawler": "3.1.*"

},
"autoload": {
    "classmap": [
        "database"
    ],
    "files":[
      "app/Helpers/helpers.php"
    ],
    "psr-4": {
        "App\\": "app/",
        "Lufficc\\": "app/Lufficc/"
    }
},
"autoload-dev": {
    "classmap": [
        "tests/TestCase.php"
    ]
},
"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"
    ]
},
"config": {
    "preferred-install": "dist"
},
    "minimum-stability": "dev",
    "prefer-stable": true
}

现在通过将以下代码添加到我的composer.json文件

来解决

"repositories": [
{
     "type": "composer",
     "url": "https://packagist.org"
},
{ "packagist": false }
]