title: Rails Backup Gem fails to backup replicated PostgreSQL database on slave with pg_dump permission error
body: <p>Running backup fails with the following error:</p>
  
  <pre><code>pg_dump: Error message from server: ERROR:  canceling statement due to conflict with recovery
  DETAIL:  User query might have needed to see row versions that must be removed.
  Errno::EPERM: Operation not permitted - 'pg_dump' returned exit code: 1
  </code></pre>
  
  <p>even though the user has permissions to access pg_dump on the database</p>
  
  <p>This is a replicated database and the backup process is running on the slave.</p>