无法将 Bootstrap 4 SCSS 导入 Angular-Cli 1.5

我刚刚将我的 CLI 项目升级到了 Angular 5/CLI 1.5，无论我做什么，我都会收到来自 Bootstrap 4 的错误。这是主要错误：

ERROR in ./node_modules/css-loader?{"sourceMap":false,"importLoaders":1}!./node_modules/postcss-loader?{"ident":"postcss"}!./node_modules/sass-loader/lib/loader.js?{"sourceMap":false,"precision":8,"includePaths":[]}!./src/styles.scss
Module build failed:
  @return mix($color-base, $color, $level * $theme-color-interval);
         ^
      Argument `$color-2` of `mix($color-1, $color-2, $weight: 50%)` must be a color

我的 Bootstrap 安装基本上是通过 scss 导入我想要的东西，而不是全部。

一直在工作的导入：

@import "~bootstrap/scss/functions";
@import "~bootstrap/scss/variables";
@import "~bootstrap/scss/mixins";
@import "~bootstrap/scss/reboot";
@import "~bootstrap/scss/bootstrap-grid";
@import "~bootstrap/scss/tables";
@import "~bootstrap/scss/alert";
@import "~bootstrap/scss/utilities";

我也试过导入整个东西来调试问题，但出现了同样的错误：

@import "~bootstrap/scss/bootstrap";

我已经阅读了有关此问题的旧线程，说它很久以前就已修复，但我无法绕过它。有没有人遇到过这个问题并解决了？

工作流程：

• 删除 node_modules 和 package-lock.json
• npm install
• ng serve （我使用的是全局 CLI，而不是本地的）

节点版本：8.9.0

NPM 版本：5.5.1

这是我的设置：

"dependencies": {
    "@angular/animations": "^5.0.0",
    "@angular/cdk": "^5.0.0-rc0",
    "@angular/cli": "^1.5.0",
    "@angular/common": "^5.0.0",
    "@angular/compiler": "^5.0.0",
    "@angular/compiler-cli": "^5.0.0",
    "@angular/core": "^5.0.0",
    "@angular/forms": "^5.0.0",
    "@angular/http": "^5.0.0",
    "@angular/language-service": "^5.0.0",
    "@angular/material": "^5.0.0-rc0",
    "@angular/platform-browser": "^5.0.0",
    "@angular/platform-browser-dynamic": "^5.0.0",
    "@angular/platform-server": "^5.0.0",
    "@angular/router": "^5.0.0",
    "bootstrap": "^4.0.0-beta.2",
    "core-js": "^2.4.1",
    "font-awesome": "^4.7.0",
    "hammerjs": "^2.0.8",
    "lodash": "^4.17.4",
    "rxjs": "^5.5.2",
    "socket.io-client": "^2.0.4",
    "zone.js": "^0.8.18"
  },

"devDependencies": {
    "@types/jasmine": "~2.5.53",
    "@types/jasminewd2": "~2.0.2",
    "@types/lodash": "^4.14.77",
    "@types/node": "~8.0.5",
    "codelyzer": "~4.0.1",
    "jasmine-core": "~2.6.2",
    "jasmine-spec-reporter": "~4.1.0",
    "karma": "~1.7.0",
    "karma-chrome-launcher": "~2.1.1",
    "karma-cli": "~1.0.1",
    "karma-coverage-istanbul-reporter": "^1.2.1",
    "karma-jasmine": "~1.1.0",
    "karma-jasmine-html-reporter": "^0.2.2",
    "protractor": "~5.1.2",
    "ts-node": "~3.3.0",
    "tslint": "~5.7.0",
    "typescript": "~2.4.2"
  }