title: Unable to generate a URL for "page_slug", after creating a user
body: <p>I have a strange problem. I installed and configured SonataUserBundle to work with FosUserBundle and SonataAdminBundle. The installed went without any problems and everything seems to be working perfectly, except when I create another user via sonataUserBundle web page. Once I create the user (and it is created when I look in the database), I cannot see the users list anymore. When I click to return to the users list, I get the following error:</p>
  
  <pre><code>An exception has been thrown during the rendering of a template ("Unable to generate a URL for the named route "page_slug" as such route does not exist.") in "SonataAdminBundle:CRUD:list.html.twig".
  </code></pre>
  
  <p>If I delete the user from the database, to only have one user, then I can access the users list.</p>
  
  <p>I have absolutely no clue on how to get further on how to resolve this issue...</p>
  
  <p>Edit 1:</p>
  
  <p>I found out, thanks to Marko Jurinčič that I have these lines in my config </p>
  
  <pre><code>sonata_user:
  
      impersonating:
          route:                page_slug
          parameters:           { path: / }
  </code></pre>
  
  <p>However, this doesn't look like a route and effectively, there are no routes named page_slug whatsoever. Is it supposed to have a route name "page_slug" ?</p>