class Bundler::RubygemsIntegration

def replace_gem(specs)
  reverse_rubygems_kernel_mixin
  executables = specs.map { |s| s.executables }.flatten
  ::Kernel.send(:define_method, :gem) do |dep, *reqs|
    if executables.include? File.basename(caller.first.split(':').first)
      return
    end
    reqs.pop if reqs.last.is_a?(Hash)
    unless dep.respond_to?(:name) && dep.respond_to?(:requirement)
      dep = Gem::Dependency.new(dep, reqs)
    end
    spec = specs.find  { |s| s.name == dep.name }
    if spec.nil?
      e = Gem::LoadError.new "#{dep.name} is not part of the bundle. Add it to Gemfile."
      e.name = dep.name
      if e.respond_to?(:requirement=)
        e.requirement = dep.requirement
      else
        e.version_requirement = dep.requirement
      end
      raise e
    elsif dep !~ spec
      e = Gem::LoadError.new "can't activate #{dep}, already activated #{spec.full_name}. " \
                             "Make sure all dependencies are added to Gemfile."
      e.name = dep.name
      if e.respond_to?(:requirement=)
        e.requirement = dep.requirement
      else
        e.version_requirement = dep.requirement
      end
      raise e
    end
    true
  end
end