'Cause a users.username dependency failure.'

def testKnowledgeBaseRetrievalLinuxNoUsers(self):

    self.ClearKB()
    with test_lib.ConfigOverrider({'Artifacts.knowledge_base': ['NetgroupConfiguration', 'NssCacheLinuxPasswdHomedirs', 'LinuxRelease'], 'Artifacts.netgroup_filter_regexes': ['^doesntexist$']}):
        with vfs_test_lib.VFSOverrider(rdf_paths.PathSpec.PathType.OS, vfs_test_lib.FakeTestDataVFSHandler):
            for _ in flow_test_lib.TestFlowHelper(artifact.KnowledgeBaseInitializationFlow.__name__, self.client_mock, require_complete=False, client_id=self.client_id, token=self.token):
                pass
            client = aff4.FACTORY.Open(self.client_id, token=self.token, mode='rw')
            kb = artifact.GetArtifactKnowledgeBase(client)
            self.assertEqual(kb.os_major_version, 14)
            self.assertEqual(kb.os_minor_version, 4)
            self.assertItemsEqual([x.username for x in kb.users], [])
