title: Server side validation without closing JQuery (bootstrap) Dialog
body: <p>I want to create a login form in HTML that will do some server side validation of the fields.</p>
  
  <p>In other words:</p>
  
  <ol>
  <li>User clicks Log In button inside the dialog </li>
  <li>Code sends data to
  server to validate. </li>
  <li>Login dialog does not go away (but ideally shows
  some progress indicator) </li>
  <li>If valid, goes to a new page. Otherwise
  dialog stays up and displays an error message</li>
  </ol>
  
  <p>If using AJAX please also include server code, ideally in Python. But prefer not to use AJAX.</p>
  
  <p>(I've read some some similar questions but I'm not clear if the are the same as what I want.)</p>