'Create fake filesystem.'

def setUp(self):

    super(GRRTempFileTestFilename, self).setUp()
    self.client_tempdir = tempfile.mkdtemp(dir=config.CONFIG.Get('Client.tempdir_roots')[0])
    self.tempdir_overrider = test_lib.ConfigOverrider({'Client.tempdir_roots': [os.path.dirname(self.client_tempdir)], 'Client.grr_tempdir': os.path.basename(self.client_tempdir)})
    self.tempdir_overrider.Start()
