App backtraces, even when testing javascript.

backtrace.rb

ApplicationController.class_eval do
  rescue_from StandardError do |exception|
    $stderr.puts ExceptionFormatter.summarize exception
    raise
  end
end

class ExceptionFormatter
  extend Cucumber::Term::ANSIColor
  def self.summarize(e)
    unless Capybara.current_driver == :rack_test
      relative_path_starts_at = Rails.root.to_s.size
      trace = e.backtrace.grep(Regexp.new Rails.root.to_s).map {|line| line[relative_path_starts_at..-1] }
      red "#{e}\n#{trace.join "\n" }\n"
    end
  end
end