帮我看下xml

我在做planetlab平台,最后测试时,从各个节点返回下面的信息,我完全用文档的测试实例,我不知道哪出错了,
<?xml version='1.0'?>
<methodResponse>
<fault>
<value><struct>
<member>
<name>faultCode</name>
<value><int>1</int></value>
</member>
<member>
<name>faultString</name>
<value><string>&lt;class 'xml.parsers.expat.ExpatError'&gt;:no element found: line 1, column 0</string></value>
</member>
</struct></value>
</fault>
</methodResponse>
测试实例:
#!/usr/bin/python
### phonehome.py
### Hello World demonstration script
phonehome_url = "http://www.your.url/~username/hw_demo/phonehome.php"
import sys, urllib, xmlrpclib, socket
api_server = xmlrpclib.ServerProxy('https://www.planet-lab.org/PLCAPI/')
auth = {}
auth['AuthMethod'] = "anonymous"
auth['Role'] = "user"
hostname = socket.gethostname()
query = api_server.GetNodes(auth,
{'hostname': hostname}, ['site_id'])
site_id = query[0]['site_id']
site_info = api_server.GetSites(auth,
{'site_id': site_id}, ['site_id', 'name', 'url',
'latitude', 'longitude', 'login_base'])
site_info = urllib.urlencode(site_info[0])
urllib.urlopen(phonehome_url, site_info)
谁告诉下啊,我的email:jimsong@mail.ustc.edu.cn