Upgrade to latest version of Vagrant.
After installation, the following messages appear whenever vagrant runs.
These were already present in previous versions, I'm not sure if/what
to do about them:
Ignoring ffi-1.9.18 because its extensions are not built. Try: gem pristine ffi --version 1.9.18
Ignoring unf_ext-0.0.7.4 because its extensions are not built. Try: gem pristine unf_ext --version 0.0.7.4
Ignoring wdm-0.1.1 because its extensions are not built. Try: gem pristine wdm --version 0.1.1
9bcd1de373