[poky] question about yoctoproject mirrors

[Foinel]

Hello,
I'm trying to use the denzil branch and encounter some issues with a
package. netbase to be more precise. On upstream, netbase 4.47 does
not exist anymore. So it automatically tries a mirror to download
netbase 4.47. It ends up fetching the package from
http://snapshot.debian.net/archive/pool/n/netbase/netbase_4.47.tar.gz
. The package from this mirror seems broken though and do_unpack fails
with "gzip: stdin: not in gzip format"
Now my question is: why doesn't it uses
http://downloads.yoctoproject.org/mirror/sources/ ? Which is the
scenario when it fetches from the yoctoproject mirror?

Thanks.