Error page not recognisable in body classes [5.2]

[mauritsvanrees]

In Plone 4.3, on an error page, you have in the body classes: template-default_error_message.
In Plone 5.2, you get template-index-html. That can indicate lots of possible templates/views.
It would be useful to be able to recognise an error page again, for example for Diazo rules.
The exact same body class is not needed.