[BUGFIX] Error handler makes impossible fix #2775205

Problem/Motivation

At this moment, the error handler is catching all errors that are more important than a notice. In order to implement #2775205: [PP-2] [FEATURE] Discus how to make JSON API use text input formats for long text fields we need to be able to accept notices created by Drupal\Component\Utility\HTML::load().

Proposed resolution

Raise an exception for errors more important than notices.

Remaining tasks

Write a patch.

User interface changes

None

API changes

None