STY: PEP8/pyflakes clean Filter
STY: PEP8/pyflakes clean HTTPDownloader (except apparently unused encodings imports)
STY: PEP8/pyflakes clean BT1/__init__ and makemetafile
STY: PEP8/pyflakes clean NatCheck
STY: PEP8/pyflakes clean PiecePicker
STY: PEP8/pyflakes clean Rerequester