Sporadic "directory not empty" errors when using new-build

[DanielG]

While new-build is installing dependencies I get errors similar to the following every couple of builds, it's very hard to reproduce, seems to be made more likely to happen when using a large -j though.

cabal: Failed to build <something-1.2.3.4> (which is required by <pkg> and
<pkg>). The failure occurred during the final install step. The
exception was:
<somewhere>/dist-newstyle/tmp/package-registration--64315:
removeDirectoryRecursive: unsatisfied constraints (Directory not empty)

I've had this happen on both Debian jessie as well as CentOS 6, with btrfs on one and NFS on the other.

[DanielG]

I can't reproduce this anymore with the 2.0 branch, seems to be fixed.