def Verify(self, hvparams=None):
    """Verify the hypervisor.

    For the fake hypervisor, it just checks the existence of the base
    dir.

    @type hvparams: dict of strings
    @param hvparams: hypervisor parameters to be verified against; not used
      for fake hypervisors

    @return: Problem description if something is wrong, C{None} otherwise

    """
    if os.path.exists(self._ROOT_DIR):
      return None
    else:
      return self._ROOT_DIR % "The required directory '%s' does not exist"
dataset/ETHPy150Open ganeti/ganeti/lib/hypervisor/hv_fake.py/FakeHypervisor.Verify/swapped operands of `%`