tweak_backtrace

# File lib/spec/runner/backtrace_tweaker.rb, line 41
      def tweak_backtrace(error)
        return if error.backtrace.nil?
        error.backtrace.collect! do |line|
          clean_up_double_slashes(line)
          IGNORE_PATTERNS.each do |ignore|
            if line =~ ignore
              line = nil
              break
            end
          end
          line
        end
        error.backtrace.compact!
      end