Change record status: 
Project: 
Introduced in branch: 
8.3.x
Introduced in version: 
8.3.0
Description: 

Changes the response for some invalid request bodies that cause 400 responses: they'll change from

['error' => 'THE ERROR MESSAGE']

to:

['message' => 'THE ERROR MESSAGE']

See #2813853: RequestHandler has its own error handling rather than leaving it to KernelEvents::EXCEPTION event subscribers for details.

Impacts: 
Module developers
Themers
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