code: def _up_to_date(md5, fn):
      
      if os.path.exists(fn):
          if hashlib.md5(open(fn).read()).hexdigest() == md5:
              logger.info('md5sum match for %s' % fn)
              return True
          else:
              logger.info('wrong md5sum for %s' % fn)
              os.unlink(fn)
docs: Make sure md5sum(fn) == md5, and if not, delete `fn`.