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
Updates Done (doc team, etc.)
Online documentation: 
Not done
Theming guide: 
Not done
Module developer documentation: 
Not done
Examples project: 
Not done
Coder Review: 
Not done
Coder Upgrade: 
Not done
Other: 
Other updates done