Get the state(s) of an account at a particular point in history
        Returns [{...}]

def GET_account_at(self, path_info, account_addr, block_height):
        """
        Get the state(s) of an account at a particular point in history
        Returns [{...}]
        """
        if not check_account_address(account_addr):
            return self._reply_json({'error': 'Invalid address'}, status_code=400)

        try:
            block_height = int(block_height)
            assert check_block(block_height)
        except:
            return self._reply_json({'error': 'Invalid block height'}, status_code=400)

        blockstackd_url = get_blockstackd_url()
        res = blockstackd_client.get_account_at(account_addr, block_height, hostport=blockstackd_url)
        if json_is_error(res):
            log.error("Failed to list account history for {} at {}: {}".format(account_addr, block_height, res['error']))
            return self._reply_json({'error': 'Failed to get account state for {} at {}'.format(account_addr, block_height)}, status_code=res.get('http_status', 500))

        self._reply_json(res)
        return