Kraken交换私人休息呼叫返回'；无效参数'；python

我一直在尝试使用Kraken Exchange REST私有API，但在获得非“内部错误”的响应时遇到了问题

以下是用于发送请求的代码：

class Kraken_Harness:
    def __init__(self, apiPublicKey="", apiPrivateKey="", timeout=10):
        self.apiPath = 'https://api.kraken.com'
        self.apiPublicKey = apiPublicKey
        self.apiPrivateKey = apiPrivateKey
        self.timeout = timeout
        self.nonce = 0

   def sign_message(self, endpoint, postData, nonce=""):
        
        apiPostData = 'nonce=' + nonce + '&' + postData

        # Decode API private key from base64 format displayed in account management
        api_secret = base64.b64decode(self.apiPrivateKey)

        # Cryptographic hash algorithms
        sha256_hash = hashlib.sha256(nonce.encode('utf-8') + apiPostData.encode('utf-8')).digest()

        hmac_sha256_data = endpoint.encode('utf-8') + sha256_hash
        hmac_sha256_hash = hmac.new(api_secret, hmac_sha256_data, hashlib.sha512)
        
        # Encode signature into base64 format used in API-Sign value
        api_signature = base64.b64encode(hmac_sha256_hash.digest())
        # pdb.set_trace()
        
        # API authentication signature for use in API-Sign HTTP header
        return api_signature

    # creates a unique nonce
    def get_nonce(self):
        # https://en.wikipedia.org/wiki/Modulo_operation
        self.nonce = (self.nonce + 1) & 8191
        return str(int(time.time() * 1000)) + str(self.nonce).zfill(4)

    # sends an HTTP request
    def make_request(self, endpoint, postUrl=""):
        # create authentication headers
        # krakent requires the header to have an
        #   APIKey
        #   Nonce
        #   Authenticator

        nonce = self.get_nonce()
        signature = self.sign_message(endpoint, postUrl, nonce=nonce)
        authentHeaders = {"API-Key": self.apiPublicKey,
                            "nonce": nonce, "API-Sign": signature}

        authentHeaders["User-Agent"] = "Kraken REST API"

        # create request
        if postUrl != "":
            url = self.apiPath + endpoint + "?" + postUrl
        else:
            url = self.apiPath + endpoint
        request = urllib2.Request(url, str.encode(postUrl), authentHeaders)
        response = urllib2.urlopen(request, timeout=self.timeout)

        # return
        return response.read().decode("utf-8")

    def get_accountbalance(self):
        """
        Returns:
            array of asset names and balance amount
        """
        endpoint = '/0/private/Balance'
        return self.make_request(endpoint)

我的留言签名可能是错的吗？你知道内部错误是什么意思吗