Allow Package/Index file with an empty extension

When downloading Index files during an "update" operation there are
often "Index" files without an extension at all. So additionally to
"Index" extensions like: .gz, .lzma, .bz2 also try to download a
file/package without any filename extension.
I would prefer a different name thant 'None'. I believe None is already a keyword in Python.

Also, can you please paste the application output after this patch? I'd like to see how it looks. Thanks