Comment 17 for bug 1559420

The one-line quick fix for vagrant bundler.rb is as follows:

    sudo sed -i'' "s/Specification.all = nil/Specification.reset/" /usr/lib/ruby/vendor_ruby/vagrant/bundler.rb

Source: https://github.com/vagrant-libvirt/vagrant-libvirt/issues/575#issuecomment-231612940