Problem/Motivation
When the batch API was converted into OO syntax the functionality was left as it was in Drupal 8.3 and before. Because of this an error can happen if the file passed into setFile() does not exist.
Proposed resolution
Update the the code in core/lib/Drupal/Core/Batch/Batch.php, as well as other files, to ensure the file exists and log the problem and throw an exception if it does not.
Remaining tasks
- Update the code
User interface changes
None
API changes
None
Data model changes
None