def wait_log(regexp)
      cursor = 0
      Timeout::timeout(10) do
        loop do
          line = @loglines[cursor]
          sleep(10e-3) if line.nil?
          break if line && line =~ regexp
          cursor += 1 unless line.nil?
        end
      end
      self
    end
def wait_log(regexp)
      cursor = 0
      Timeout::timeout(10) do
        loop do
          line = @loglines[cursor]
          sleep(10e-3) if line.nil?
          break if line && line =~ regexp
          cursor += 1 unless line.nil?
        end
      end
      self
    end
wait until a log line is seen that matches `regexp`, up to a timeout