'export_download( self, trans, id, jeha_id )
* GET /api/histories/{id}/exports/{jeha_id}:
If ready and available, return raw contents of exported history.
Use/poll "PUT /api/histories/{id}/exports" to initiate the creation
of such an export - when ready that route will return 200 status
code (instead of 202) with a JSON dictionary containing a
`download_url`.'

@expose_api_raw
def archive_download(self, trans, id, jeha_id, **kwds):

    history = self.history_manager.get_accessible(self.decode_id(id), trans.user, current_history=trans.history)
    matching_exports = [e for e in history.exports if (trans.security.encode_id(e.id) == jeha_id)]
    if (not matching_exports):
        raise exceptions.ObjectNotFound()
    jeha = matching_exports[0]
    if (not jeha.ready):
        raise exceptions.MessageException('Export    not    available    or    not    yet    ready.')
    return self.serve_ready_history_export(trans, jeha)
