Internationalization for public errors
    
    Currently, we throw many public exceptions without proper i18n.
    Wrap natural-language error messages in _() so they can be translated.
    
    In the service plugin, raise NotFound errors using handle_not_found helper
    so the error message contains the offending service.
    
    Use ScriptError instead of NotFoundError in bindinstance install.
    
    https://fedorahosted.org/freeipa/ticket/1953