How to get the reason (error) of TC failure on fly using Ruby + Rspec

I am trying to do some specific logic in "after (:each)" declarations for failed TCs. How to catch the fact and the reason of TC failure using Ruby and Rspec methods? I tried something like:

  after(:each) do
    if RSpec::Expectations::ExpectationNotMetError
      e = RSpec::Expectations::ExpectationNotMetError
      puts "Error is: " + e.to_s
      @driver.save_screenshot "../Reports/#{e}.png"
    end
  end

But it doesn't work.