Change error code severity for syslog?

The Postgres errors when sent to syslog have their severity levels translated as follows:

I have a system which raises an alert every time syslog receives an ERROR (or higher severity level). 

For most of the Postgres errors, translating it to WARNING level in syslog works, however, I wanted to translate ERROR codes XX000/1/2 in Postgres to be ERROR in syslog as well, so that it triggers the alert system and I can notified.

Is there any way to change the severity level for these specific error codes in Postgres?

Thanks