The problem is that commmondatastorage.googleapis.com doesn't handle non-existing stuff in standard way, so instead of returning code 404 when it cannot find the data it will return non-sensical XML document.
All that said your problem lies in incorrect binhost being used to download required packages. What I tried was this:
dev_install --binhost=https://commondatastorage.googleapis.com/chromeos-prebuilt/board/daisy/full-15.11.12.140004/packages
Unfortunately this doesn't solve the issue really since that binhost doesn't have python-2.6.8.tbz2 which is needed in later parts of installation. It's still a good start for investigation though I believe