Don't allow attachment filenames with weird ASCII-8 bytes.
Don't allow attachment filenames with weird ASCII-8 bytes.

This causes attachments to fail to be created. Very weird.

YOTOV-LIMITED/whitehall,alphagov/whitehall,hotvulcan/whitehall,alphagov/whitehall,robinwhittleton/whitehall,YOTOV-LIMITED/whitehall,ggoral/whitehall,askl56/whitehall,askl56/whitehall,askl56/whitehall,robinwhittleton/whitehall,hotvulcan/whitehall,hotvulcan/whitehall,robinwhittleton/whitehall,ggoral/whitehall,ggoral/whitehall,YOTOV-LIMITED/whitehall,alphagov/whitehall,YOTOV-LIMITED/whitehall,hotvulcan/whitehall,ggoral/whitehall,alphagov/whitehall,robinwhittleton/whitehall,askl56/whitehall