ports/74956: net/py-bittornado fails checksum on last piece & hard crash on exit on amd64

[Axel Gonzalez]

regarding the commit for:

PR: ports/75191


this seems to fix the crash problem... tried several times, and it exits 
normally.


Still there is the last piece problem.

It tries to download last piece again and again, and it never ends.

If you quit the program, and resume the download (only last piece missing), it 
finishes almost immediately, with no re-downloads.

to rule out bad sources, i tried 5.3-RELEASE-amd64-bootonly.torrent ... this 
has only one seed, so i download from one source only.. and teh problem is 
the same.

Greetings!