Since Zope 4, the `standard_error_message` is rendered in the context
of REQUEST['PUBLISHED'], which in case of publishing a skin (page
template or script) in the context of a document is is the skin itself,
but for error rendering in case of erp5_web Web Site or Web Section,
we expect standard_error_message_template to always be rendered in the
context of the document, that's why we use REQUEST.PARENTS[0] as context.

REQUEST.PUBLISHED = <PythonScript at /erp5/script used for /erp5/module/document>
REQUEST.PARENTS [<Document>, <Module>, <ERP5Site>, ...]