- only download Release files once and not by apt as well as with curl
and thus avoid a mirror push happening between both downloads
- no heuristic needed to place the file in their correct mirror
location
- no manual checksum checking
- only throttle download speed when actually downloading and not when
retrieving files from the cache
- no translation of filenames between how the epoch colon is stored in
files in /var/cache/apt/archives versus how it is stored in files on
the mirrors
- no special handling of stable update and security mirrors
- implemented in Python instead of shell and thus an order of magnitude
faster
