erp5_xhtml_style: Fix logged_in handling of came_from when authentication failed.

Also, modernise it a bit.

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

@@ -4,14 +4,23 @@ if portal.portal_skins.updateSkinCookie():
 url = REQUEST.get("came_from")
 if portal.portal_membership.isAnonymousUser():
   RESPONSE.expireCookie("__ac", path="/")
-  url = "%s/login_form?portal_status_message=%s" % (
-    context.absolute_url(),
-    context.Base_translateString("Login and/or password is incorrect.")
-    + ("&came_from=" + url if url else ""))
-elif not url:
+  keep_item_dict = {
+    'portal_status_message': context.Base_translateString("Login and/or password is incorrect."),
+  }
+  if url:
+    keep_item_dict['came_from'] = url
+  context.Base_redirect(
+    form_id='login_form',
+    keep_items=keep_item_dict,
+  )
+  return
+if not url:
   url = context.absolute_url()
 topmost_url_document = context.Base_getURLTopmostDocumentValue()
 if not topmost_url_document.isURLAncestorOf(url):
-  return context.ERP5Site_redirect(topmost_url_document.absolute_url(),
-    keep_items={'portal_status_message': 'Redirection to an external site prevented.'})
+  return topmost_url_document.Base_redirect(
+    keep_items={
+      'portal_status_message': context.Base_translateString('Redirection to an external site prevented.'),
+    }
+  )
 return RESPONSE.redirect(url)