One more fix on upload_index_network_cached for python3 compatibility.

src/zc/buildout/networkcache.py

@@ -245,7 +245,7 @@ def upload_index_network_cached(dir_url, cache_url, external_url, base, requirem
 
     import tempfile
     f = tempfile.TemporaryFile()
-    f.write(content)
+    f.write(content.encode())
 
     # convert '' into None in order to call nc nicely
     if not signature_private_key_file: