shutil.copyfileobj has default buffer.

src/zc/buildout/networkcache.py

@@ -80,10 +80,9 @@ def download_network_cached(dir_url, cache_url, path, url, logger,
                signature_certificate_file_list=signature_certificate_file_list)
         file_descriptor = nc.select(directory_key)
 
-        buffer_size = min(1024, os.path.getsize(file_descriptor.name))
         f = open(path, 'w+b')
         try:
-            shutil.copyfileobj(file_descriptor, f, buffer_size)
+            shutil.copyfileobj(file_descriptor, f)
         finally:
             f.close()
             file_descriptor.close()