Session optimization (#3423)

frontend/src/components/session-expired-tip.js

@@ -0,0 +1,12 @@
+import React from 'react';
+import { gettext, loginUrl } from '../utils/constants';
+
+function SessionExpiredTip() {
+  return(
+    <span className="session-expired-tip">{gettext('You are log out.')}{' '}
+      <a className="action-link session-expired-link" href={`${loginUrl}?next=${encodeURIComponent(location.href)}`}>{gettext('Login again.')}</a>
+    </span>
+  )
+} 
+
+export default SessionExpiredTip