'Ensures the command does not fail if specified groups cannot be found.'

def test_nonexistent_group(self):

    user = User.objects.create(username=TEST_USERNAME, email=TEST_EMAIL)
    groups = {}
    for group_name in 'abc':
        groups[group_name] = Group.objects.create(name=group_name)
        user.groups.add(groups[group_name])
    call_command('manage_user', TEST_USERNAME, TEST_EMAIL, '-g', 'b', 'c', 'd')
    actual_groups = [group.name for group in user.groups.all()]
    self.assertEqual(actual_groups, ['b', 'c'])
