class Gem::Resolver::Conflict

def request_path(current)
  path = []
  while current do
    case current
    when Gem::Resolver::ActivationRequest then
      path <<
        "#{current.request.dependency}, #{current.spec.version} activated"
      current = current.parent
    when Gem::Resolver::DependencyRequest then
      path << "#{current.dependency}"
      current = current.requester
    else
      raise Gem::Exception, "[BUG] unknown request class #{current.class}"
    end
  end
  path = ['user request (gem command or Gemfile)'] if path.empty?
  path
end