Remove broken fallback directory mirrors
Some time around 0.3.0.?-rc, we should remove all non-functional fallback directories from the December 2016 list (or rebuild the entire list).
I'll create a draft branch here, but the script should be re-run just before the release (and ideally, operators should be contacted and given an opportunity to fix any errors).
To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information