This is a bit of a doozy to debug since the error is fully in a pip subprocess - no Pants or Pex involved at that point. Is https://pypi.cbhq.net, perchance an insternal pypi repo we could leverage? The simplest workaround is to build a macOS wheel once - by hand, and upload it there. It looks like fastparquet only publishes pre-built wheels for Linux and Windows and so the mac users are being forced to build the wheel locally and hitting this error.