tweak_backtrace

# File lib/spec/runner/backtrace_tweaker.rb, line 10
      def tweak_backtrace(error)
        return if error.backtrace.nil?
        tweaked = error.backtrace.collect do |line|
          clean_up_double_slashes(line)
          line
        end
        error.set_backtrace(tweaked)
      end