title: 'Error: Please install pg package manually' in js console after running npm run serve
body: <p>After running <code>npm run serve</code> to start my Vue web app, it starts fine, but the page doesn't load and I see the following in the console.</p>
  
  <pre><code>Error: Please install pg package manually
  _loadDialectModule connection-manager.js:81
  ConnectionManager connection-manager.js:18
  PostgresDialect index.js:14
  Sequelize sequelize.js:322
  &lt;anonymous&gt; main.js:32
  js app.js:11203
  \__webpack_require__ app.js:770
  fn app.js:130
  1 app.js:11265
  \__webpack_require__ app.js:770
  &lt;anonymous&gt; app.js:908
  &lt;anonymous&gt; app.js:911
  </code></pre>
  
  <p>I've already tried installing pg and pg-hstore both locally and globally.</p>
  
  <pre><code>npm install --save pg pg-hstore
  </code></pre>
  
  <pre><code>npm install --save -g pg pg-hstore
  </code></pre>
  
  <p>Below is part of my main.js file to test sequelize.</p>
  
  <pre><code>const Sequelize = require("sequelize");
  const sequelize = new Sequelize(
    "postgres://USER:PASSWORD@localhost:5432/DBNAME"
  );
  
  sequelize
    .authenticate()
    .then(() =&gt; {
      // eslint-disable-next-line no-console
      console.log("Connection has been established successfully.");
    })
    .catch(err =&gt; {
      // eslint-disable-next-line no-console
      console.error("Unable to connect to the database:", err);
    });
  </code></pre>