'Returns the relative path name for the given error handler.
Args:
error_handler: an app_engine_web_xml.ErrorHandler.
Returns:
the relative path name for the handler.
Raises:
AppEngineConfigException: if the named file is not an existing static
file.'

def ErrorHandlerPath(self, error_handler):

    name = error_handler.name
    if (not name.startswith('/')):
        name = ('/' + name)
    path = ('__static__' + name)
    if (path not in self.static_files):
        raise AppEngineConfigException(('No    static    file    found    for    error    handler:    %s,    out    of    %s' % (name, self.static_files)))
    return path
