Error: File to import not found or unreadable: ~bootstrap/scss/bootstrap

I followed the instructions at getbootstrap.com thinking that everything would just work. It isn’t so far :

Everything seems to be fine until I try to load the page, at which point my Express.js app throws the error

    [[sass] error: File to import not found or unreadable: ~bootstrap/scss/bootstrap. 
Parent style sheet: .../sass/app.scss at options.error (.../node-sass/lib/index.js:291:26)

I have tried npm install, restarting my server, looking on Google, StackOverflow (yes, I know there are quite a few similar questions, but none of them answer my question), the Bootstrap 4 GitHub issue pages and so far I haven’t been able to come up with the answer.

Could it be that I installed the dependencies in the wrong place? (Dev instead of production or vis-à-vis)

Why am I getting this error??

My webpack.config.js file looks like this…

 module.exports = {
  entry: './src/index.js',
  output: {
    path: __dirname + '/public',
    filename: 'bundle.js'
  },
  module: {
    loaders: [
      {
        test: /.json$/,
        loader: 'json-loader'
      },
      {
        test: /.js$/,
        loader: 'babel-loader'
      },
      {
        test: /.(scss)$/,
        use: [{
          loader: 'style-loader', // inject CSS to page
        }, {
          loader: 'css-loader', // translate CSS into CommonJS modules
        }, {
          loader: 'postcss-loader', // run post CSS actions
          options: {
            plugins: function () { // post css plugins, can be exported to postcss.config.js
              return [
                require('precss'),
                require('autoprefixer')
              ];
            }
          }
        }, {
          loader: 'sass-loader' // compile Sass to CSS
        }]
      }
    ]
  }
};

My package.json file

...
"scripts": {
    "start": "nodemon --exec babel-node server.js --ignore public/",
    "dev": "webpack -wd",
    "test": "echo "Error: no test specified" && exit 1"
  },
"dependencies": {
    "axios": "^0.17.1",
    "bootstrap": "^4.0.0",
    "ejs": "^2.5.7",
    "express": "^4.16.2",
    "jquery": "^3.3.1",
    "mongoose": "^5.0.0",
    "node-sass-middleware": "^0.11.0",
    "popper.js": "^1.12.9",
    "precss": "^3.1.0",
    "react": "^16.2.0",
    "react-dom": "^16.2.0"
  },
  "devDependencies": {
    "autoprefixer": "^7.2.5",
    "babel-cli": "^6.26.0",
    "babel-eslint": "^8.2.1",
    "babel-loader": "^7.1.2",
    "babel-preset-env": "^1.6.1",
    "babel-preset-react": "^6.24.1",
    "babel-preset-stage-2": "^6.24.1",
    "css-loader": "^0.28.9",
    "eslint": "^4.15.0",
    "eslint-plugin-react": "^7.5.1",
    "node-sass": "^4.7.2",
    "nodemon": "^1.14.11",
    "postcss-loader": "^2.0.10",
    "sass-loader": "^6.0.6",
    "style-loader": "^0.19.1",
    "webpack": "^3.10.0"
  }
}

postcss.config.js

module.exports = {
  plugins: [
    require('autoprefixer')
  ]
};

and inside app.scss I have

@import "custom";
@import "~bootstrap/scss/bootstrap";

Answer

When Sass is precompiled by its own CLI, it processes @imports by itself, and sometimes thus doesn’t understand ~ notation. So you can import "node_modules/bootstrap/scss/bootstrap"; in first place and replaced the ~ notation with node_modules/ instead.