docs: def can_rewind(self):
          """ check if pg_rewind executable is there and that pg_controldata indicates
              we have either wal_log_hints or checksums turned on
          """
          # low-hanging fruit: check if pg_rewind configuration is there
          if not self.config.get('use_pg_rewind'):
              return False
  
          cmd = [self._pgcommand('pg_rewind'), '--help']
          try:
              ret = subprocess.call(cmd, stdout=open(os.devnull, 'w'), stderr=subprocess.STDOUT)
              if ret != 0:  # pg_rewind is not there, close up the shop and go home
                  return False
          except OSError:
              return False
          return self.configuration_allows_rewind(self.controldata())