title: If Operational error happens in django query in read database router, rerun the query on write database
body: <p>When a read query from read_db() router fails due to following error</p>
  <pre><code>ERROR: cancelling statement due to conflict with recovery
  Detail: User query might have needed to see row versions that must be removed
  </code></pre>
  <p>how to catch the error and retry the same query on a write db.</p>