I thought it would be clever to require a gem -- and then if it wasn't
found -- to install it automatically. I tried this for both a local gem
file and for a remote install. I wasn't able to get this to work in
either case and am now of the opinion that the Gem library isn't
designed to support this use case.

Here is one version of my code.

workspace_dir = File.join(File.dirname(__FILE__), '..', '..')
package_dir = File.join(File.dirname(__FILE__), '..', 'packages')
watir_dir = File.join(workspace_dir, 'watir')
gem_file = File.join(package_dir, 'watir-'+watir_version+'.gem')
if File.exists?(watir_dir) && use_local_watir
  $LOAD_PATH.unshift File.join(workspace_dir, 'watir')
else
  require 'rubygems'
  begin
    require_gem 'watir', '>= ' + watir_version
  rescue Gem::LoadError
    require 'rubygems/installer'
    specs = Gem::Installer.new(gem_file).install
    puts "Gem installed: #{specs}"
  end

At this point, i'm just sharing what i've learned. If any one has
reached other conclusions, i would be happy to hear about it. 

Bret