Missing directory... sometimes

[kondziu]

I tried downloading some datasets on prl-dcd. When I created them in my home directory, it ran correctly. But when I tried creating them in /mnt/data/ it complained that there isn't a /repo_clones directory. I then created the directory manually, which seems to have helped mkdir -p /mnt/data/SE1K/repo_clones.

This was difficult to diagnose because if there are more repos being downloaded, the message about what's wrong disappears, so a new user will not be able to figure it out.