无法读取实例数据，放弃 python boto 中的错误

我正在尝试使用 boto 库访问亚马逊 s3，以访问亚马逊“aws-publicdatasets”中可用的常见爬网数据。

我在 ~/.boto 中创建了访问配置文件

[Credentials]
aws_access_key_id = "my key"
aws_secret_access_key = "my_secret"

在创建与 amazon s3 的连接时，我在日志中看到以下错误。

2014-01-23 16:28:16,318 boto [DEBUG]:Retrieving credentials from metadata server.
2014-01-23 16:28:17,321 boto [ERROR]:Caught exception reading instance data
Traceback (most recent call last):
  File "/usr/lib/python2.6/site-packages/boto-2.13.3-py2.6.egg/boto/utils.py", line 211, in retry_url
    r = opener.open(req)
  File "/usr/lib64/python2.6/urllib2.py", line 391, in open
    response = self._open(req, data)
  File "/usr/lib64/python2.6/urllib2.py", line 409, in _open
    '_open', req)
  File "/usr/lib64/python2.6/urllib2.py", line 369, in _call_chain
    result = func(*args)
  File "/usr/lib64/python2.6/urllib2.py", line 1190, in http_open
    return self.do_open(httplib.HTTPConnection, req)
  File "/usr/lib64/python2.6/urllib2.py", line 1165, in do_open
    raise URLError(err)
URLError: <urlopen error timed out>
2014-01-23 16:28:17,323 boto [ERROR]:Unable to read instance data, giving up

以其他方式，我尝试在创建连接对象时提供凭据，如下所示

from boto.s3.connection import S3Connection
from boto.s3.bucket import Bucket
boto.set_stream_logger('boto')
connection = S3Connection('______','__________')    
bucket = Bucket(connection.get_bucket('aws-publicdatasets'))

我仍然在日志中看到相同的错误

在与脚本相同的文件夹中使用 .boto 文件时，我遇到了同样的错误。它必须位于主文件夹的基础上。