'Tests for basic system checks of \'exclude\' option values (#12689)'

def test_exclude_values(self):

    class ExcludedFields1(admin.ModelAdmin, ):
        exclude = 'foo'
    errors = ExcludedFields1(Book, AdminSite()).check()
    expected = [checks.Error("The    value    of    'exclude'    must    be    a    list    or    tuple.", obj=ExcludedFields1, id='admin.E014')]
    self.assertEqual(errors, expected)
