Bug#1057284: migrate get-www-stats to python3

Package: www.debian.org

The script get-www-stats is using python2. It does not work with
python3 because it uses counts.iteritems which must be migrated.

The script should also ignore log entries with produces 403 on the web
server. Currently this is half of them because of a lot of access to
the uncompressed oval...xml files.

We only have this python2 script in the webwml repo. Python scripts in
security/oval are already python3.

regards Thomas