我正在使用此链接使用python 2.7了解到S3的上传文件：
saving csv file to s3 using boto3
我在s3存储桶名称allen中有一个名为bucket的文件夹，并且我想将数据帧作为.csv文件上传到该文件夹中。
bucket='bucket/allen'
filename="output.csv"
这两个参数是Jenkins Job Scheduler的自变量。
bytes_to_write = df.to_csv(None, index = False).encode()
upload_to_s3 = s3_client.meta.client.upload_file(bytes_to_write, bucket, filename)
print "uploaded successfully"
Error: File "program.py", line 727, in <module>
upload_to_s3 = s3_client.meta.client.upload_file(bytes_to_write, args.bucket, args.filename)
File "/usr/local/lib/python2.7/dist-packages/boto3/s3/inject.py", line 131, in upload_file
extra_args=ExtraArgs, callback=Callback)
File "/usr/local/lib/python2.7/dist-packages/boto3/s3/transfer.py", line 279, in upload_file
future.result()
File "/usr/local/lib/python2.7/dist-packages/s3transfer/futures.py", line 106, in result
return self._coordinator.result()
File "/usr/local/lib/python2.7/dist-packages/s3transfer/futures.py", line 265, in result
raise self._exception
请让我知道问题出在哪里？