I downloaded the file once again a few hours later and the size changed to 5kB.I was able to install it with no error message.. I don't know why my first file was 20kB big... 

Same problem with message "% Unable to unbundle the package. It should be in tar.gz file format"But the downloaded file is only 20kB big... it looks very small for a patch...Could it be a "fake" file used to prepare the release of the real hot fix ??...