Today a new version of the Nagios/Monitoring Plugin check_esxi_hardware.py was released (20150710).
This version contains a minor change in the exit status, when a timeout or an authentication error appears. In the versions before, the plugin exited with a CRITICAL status. This doesn't really make sense as the goal of the plugin is to monitor hardware and if a defect hardware is shown, it should return a CRITICAL status. Authentication errors or connection timeouts are annoying and need to be solved, true, but the UNKNOWN status matches better for this purpose.
Thanks to Stanislav German-Evtushenko for the contribution.