do not use httplib directly, use urllib2 instead

It is not recommanded to use httplib directly, we should better
use urllib2, then this library will use httplib. This solve
issues with libnetworkcache when we try to use it behind an
http proxy.

slapos/libnetworkcache.py

@@ -20,6 +20,7 @@ import json
 import os
 import tempfile
 import urllib
+import urllib2
 import urlparse
 
 
@@ -45,7 +46,7 @@ class NetworkcacheClient(object):
 
     return_dict['path'] = parsed_url.path
     return_dict['host'] = parsed_url.hostname
-    return_dict['port'] = parsed_url.port
+    return_dict['port'] = parsed_url.port or 80
     return return_dict
 
   def __init__(self, shacache, shadir):
@@ -145,17 +146,13 @@ class NetworkcacheClient(object):
     if directory_key is not None:
       path_info = os.path.join(self.shadir_path, directory_key)
 
-    shadir_connection = httplib.HTTPConnection(self.shadir_host,
-      self.shadir_port)
+    url = "http://%s:%s%s" % (self.shadir_host, self.shadir_port, path_info)
+    request = urllib2.Request(url=url, data=None,headers=self.shadir_header_dict)
     try:
-      shadir_connection.request('GET', path_info, headers=self.shadir_header_dict)
-      result = shadir_connection.getresponse()
+      result = urllib2.urlopen(request)
       data = result.read()
-    finally:
-      shadir_connection.close()
-
-    if result.status != 200:
-      raise DirectoryNotFound(result.read())
+    except urllib2.HTTPError, error:
+      raise DirectoryNotFound("%s : %s" % (error.code, error.msg))
 
     data_list = json.loads(data)
     if len(data_list) > 1: