PHP does not validate. use Exception is declared in all other similar files in core. I will upload the patch in a minute.
Here is the little patch :)
In case you're wondering where the validation error occurs it is in core/modules/system/system.api.php line 2949.
"The thrown object must be an instance of the Exception".
This seems reasonable to me and it's a super simple patch. If you're going to extend the exception class you need to make sure it gets loaded. :)
Thanks. Committed/pushed to 8.x.
Automatically closed -- issue fixed for 2 weeks with no activity.
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