Use urlretrieve instead of httplib.

httplib does not handle the download as expected.
The implementation of urlretrieve is much better and consistent, it does
the download
writing in chunks instead of loading all the file content into memory.

Also, the httplib can easily break the file content, if the client does
not
handle it. And this lib must be very simple.

The timeout is not in favor of httplib GET method.

Based in the above reasons, httplib was replaced to
urlretrieve, once there is no reason to reimplement what already exists.

slapos/libnetworkcache/__init__.py

@@ -18,6 +18,7 @@ import hashlib
 import httplib
 import json
 import os
+from urllib import urlretrieve
 from urlparse import urlparse
 
 
@@ -54,6 +55,7 @@ class NetworkcacheClient(object):
       self.shacache_host = shacache_urlparse.hostname
       if shacache_urlparse.port is not None:
         self.shacache_host += ':%s' % shacache_urlparse.port
+    self.shacache_url = shacache
 
     # ShaDir Properties
     if shadir is not None:
@@ -134,23 +136,13 @@ class NetworkcacheClient(object):
 
     return json.loads(data)
 
-  def download(self, sha512sum):
+  def download(self, path, sha512sum):
     ''' Download the file.
     It uses http GET request method.
     '''
-    path_info = os.path.join(self.shacache_path, sha512sum)
-    shacache_connection = httplib.HTTPConnection(self.shacache_host)
-    try:
-      shacache_connection.request('GET', path_info, headers=self.shacache_header_dict)
-      result = shacache_connection.getresponse()
-      file_content = result.read()
-    finally:
-      shacache_connection.close()
-
-    if result.status != 200:
-      raise FileNotFound(result.read())
-
-    return file_content
+    sha_cache_url = os.path.join(self.shacache_url, sha512sum)
+    path, headers = urlretrieve(sha_cache_url, path)
+    return headers
 
   def select(self, directory_key=None):
     '''Download a file from shacache by selecting the entry in shadir
@@ -174,10 +166,6 @@ class NetworkcacheClient(object):
     return json.loads(data)
 
 
-class FileNotFound(Exception):
-  pass
-
-
 class DirectoryNotFound(Exception):
   pass