code: def decrypt(self, text, appid):
          
          try:
              cryptor = AES.new(self.key, self.mode, self.key[:16])
              # 使用BASE64对密文进行解码，然后AES-CBC解密
              plain_text = cryptor.decrypt(base64.b64decode(text))
          except Exception:
              return WXBizMsgCrypt_DecryptAES_Error, None
          try:
              pad = ord(plain_text[-1])
              # 去掉补位字符串
              #pkcs7 = PKCS7Encoder()
              #plain_text = pkcs7.encode(plain_text)
              # 去除16位随机字符串
              content = plain_text[16:-pad]
              xml_len = socket.ntohl(struct.unpack("I", content[:4])[0])
              xml_content = content[4:xml_len+4]
              from_appid = content[xml_len+4:]
          except Exception:
              return WXBizMsgCrypt_IllegalBuffer, None
          if from_appid != appid:
              return WXBizMsgCrypt_ValidateAppidOrCorpid_Error, None
          return 0, xml_content
docs: 对解密后的明文进行补位删除
          @param text: 密文
          @return: 删除填充补位后的明文