xhtml_style: adjust standard_error_message for Zope4

There are some few differences:

In Zope4 exceptions are callable, but we don't want to call them here,
so we use a python: expression instead of the path expression which
tries to call error_value.

error_message is sometimes not passed.

The context is different: 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>, ...]

In case of redirect, the body is no longer empty, but we explicitly
return an empty body to keep the same behavior as zope2

product/ERP5/bootstrap/erp5_xhtml_style/SkinTemplateItem/portal_skins/erp5_xhtml_style/standard_error_message.py

@@ -4,8 +4,14 @@
   it tries to render the error from the web site root. If no web site
   root is defined then it renders the error from portal.
 """
-from zExceptions import Unauthorized
+from zExceptions import Redirect, Unauthorized
+
+if isinstance(kw.get('error_value'), Redirect):
+  return ''
+
 try:
+  # Adjust exception context for Zope 4.
+  context = container.REQUEST.get('PARENTS', [context])[0]
   return context.standard_error_message_template(*args, **kw)
 except Unauthorized:
   pass

product/ERP5/bootstrap/erp5_xhtml_style/SkinTemplateItem/portal_skins/erp5_xhtml_style/standard_error_message_render.zpt

@@ -4,13 +4,13 @@
   xmlns:i18n="http://xml.zope.org/namespaces/i18n"
   metal:define-macro="standard_error_message_render"
 >
-<div tal:condition="options/error_message" tal:content="structure options/error_message" />
-<div tal:condition="not: options/error_message">
+<div tal:condition="python: options.get('error_message')" tal:content="structure options/error_message" />
+<div tal:condition="python: not options.get('error_message')">
   <h2 i18n:translate="">Site Error</h2>
   <p i18n:translate="">An error was encountered while publishing this resource.</p>
   <p>
     <strong i18n:translate="">Error Type: <span tal:replace="options/error_type" i18n:name="error_type" /></strong><br />
-    <strong i18n:translate="">Error Value: <span tal:replace="options/error_value" i18n:name="error_value" /></strong><br />
+    <strong i18n:translate="">Error Value: <span tal:replace="python: str(options['error_value'])" i18n:name="error_value" /></strong><br />
   </p>
   <hr noshade="noshade" />
   <p i18n:translate="">Troubleshooting Suggestions</p>