The Upgrader cannot start

When booting an ISO built from the feature/wheezy branch, I see an error dialog that reads:

Failed to run /usr/bin/tails-upgrade-frontend  as user tails-upgrade-frontend.

Unable to copy the user's Xauthorization file.

Original created by @intrigeri on 6903 (Redmine)

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information