torchvision 0.26 removed the torchvision.io.video submodule entirely
(only image I/O remains). The monkey-patch in install_requirements
(`torchvision.io.video.av = av`) was attempting to swap PyAV into a
torchvision-internal that no longer exists, raising AttributeError on
every FramePack run. The patch is fully vestigial against modern
torchvision; PyAV is still installed by `install('av')`, and the
sdnext save path uses PyAV directly via av.open().
Vladimir Mandic
CalamitousFelicitousness