Change record status: 
Project: 
Introduced in branch: 
8.5.x
Introduced in version: 
8.5.x-dev
Description: 

Starting from drupal 8.5.x is possible to use !severity as a valid placeholder for syslog messages.

This is not included by default in new site installations to avoid potential backward compatibility issues but site admins can configure syslog to use it.

For example:

!base_url|!timestamp|!type|!ip|!request_uri|!referer|!severity|!uid|!link|!message

Impacts: 
Site builders, administrators, editors