Pimcore provides two ways to add an error document in case something went wrong or a specific page could not be found.
1.) specify an error page in your systemsettings
2.) specify an error page per site
If you're using this plugin, you probably need some abstraction. This Bundle will help you to generate specific error documents depending on languages and/or country settings.
Just create a document called like the error page in your system settings or the error page of a specific site and place it in your tree:
site.com
- de
- error
- en
- error
- en-US
- error
site2.com
- error
The i18nBundle will search for the closest document depending on your host. If nothing could be found, the default pimcore error handling will handle the exception.