The original bug report is at: https://bugs.launchpad.net/ubuntu/+source/python-distutils-extra/+bug/770566

As you can see it had to do with a symbolic link created by distutils-extra before distutils was called upon to copy anything. Since this was done behind distutils back, LP: 770566 really was a distutils-extra problem and Martin's fix means this issue no longer arises there.

To recreate the problem in that environment distutils-extra had to be modified to coerce processing to happen in a particular order so setup.py would complete, and then results compared between an ext4 run and the build farm's presumably ext3 run. In the ext4 case the symbolic link was predictably replaced by the file itself. 

The test case I posted above should be easier to follow and doesn't involve any smoke and mirrors being done behind distutils back!

Please let me know if I provide any further information.