Check Vagrant version

Vagrantfile

MIN_REQUIRED_VAGRANT_VERSION = '1.2.1'

if Vagrant::VERSION < MIN_REQUIRED_VAGRANT_VERSION
  $stderr.puts "ERROR: We require Vagrant version >=#{min_required_vagrant_version}. Please upgrade. http://downloads.vagrantup.com/\n"
  exit 1
end

Vagrant.configure("2") do |config|
  config.vm.box = "precise64"
  config.vm.hostname = 'foo'
  config.vm.box_url = "http://files.vagrantup.com/precise64.box"
end

Yeah, this is pretty old at this point (2013?), I think this pre-dates the Vagrant.version? method:

I later found that version comparisons in Ruby are fairly simple to do with the Gem library as well:

Gem::Version.new(Vagrant::VERSION) < Gem::Version.new(MIN_REQUIRED_VAGRANT_VERSION)