title: Flash error on submitted page when there are errors from body-parser
body: <p>I have a create page which input fields and I have configured the body-parser with length restriction. When I submit the create form body-parse fails the request for length limitation which is actually right. My question is how do I flash the error message from error handler without refreshing/redirecting.</p>
  
  <p>From default error handler page I tried to flash that didn't work.
  I wanted flash message on the same page (I need the old data from the form to be intact).</p>
  
  <pre><code>    app.use((err, req, res, next) =&gt; {
      if (err &amp;&amp; err.type == 'entity.too.large' ) {
          req.flash('danger', 'Something unexpected happened!');
      } else {
          next()
      }
  });
  </code></pre>