As I understand it, the actual issue lies within rubygems:
https://github.com/rails/rails/issues/1958
https://github.com/rails/rails/commit/e7fc5d1cad27e47d3d0149a2b9a61d074c30f225
The default s.require_paths is, in as far as I can tell by the commit to fix the issue, [lib] rather than []. So you end up with lib not found errors whenever you install a gem without such a folder.
Rails in particular, but not only.
