fastdfs python客户端fdfs_client_py上传从文件问题

有人用过fdfs的python 客户端fdfs_client_py上传文件吗？我的代码如下：

     def upload_file(self,filePath=None,slaveFilePath=None): 
        #upload the apk and the apk details html file into fastdfs storage
        #apk file as master file while html file as slave file
        if filePath is None:
            return None
        ret={}
        client=Fdfs_client(self.m_clientConf)
        result=client.upload_by_filename(filePath) #upload master file
        master_fileId=''
        if result is not None: #success
            self.m_logger.info(" save %s into fdfs success"%filePath) 
            print " save %s into fdfs success"%filePath
            print result
            ret['storageIp']=result['Storage IP']
            ret['groupName']=result['Group name']
            ret['masterFileId']=result['Remote file_id']
            master_fileId=result['Remote file_id']
        print slaveFilePath,master_fileId
        if(slaveFilePath is not None): #upload slave file
            slave_res=client.upload_slave_by_filename(slaveFilePath,master_fileId,'-html')
            if slave_res is not None: #success
                self.m_logger.info(" save slave %s into fdfs success"%slaveFilePath) 
                ret['slaveFileId']=slave_res['Remote file_id']
        return ret #return the storage info

但是老是报下面的错：

从文件老是上传不成功，但是主文件却上传成功了，当我直接指定主文件id来上传从文件时，从文件却可以上传成功，有人知道怎么解决么？

文件路径不正确，这个要看fastdfs 它的参数是如何设置从文件等的。