code: def verify(self, anchors):
          
          cafile = create_temporary_ca_file(anchors)
          if cafile is None:
              return False
          try:
              cmd = self.osslcmdbase + ["-noout", "-CAfile", cafile]
              cmdres = self._apply_ossl_cmd(cmd, self.rawcrl)
          except:
              os.unlink(cafile)
              return False
          os.unlink(cafile)
          return "verify OK" in cmdres
docs: Return True if the CRL is signed by one of the provided
          anchors. False on error (invalid signature, missing anchorand, ...)