Fixed #27904 -- Added a system check that Field.validators are callable.

tests/invalid_models_tests/test_ordinary_fields.py

@@ -205,6 +205,23 @@ class CharFieldTests(TestCase):
         ]
         self.assertEqual(errors, expected)
 
+    def test_bad_validators(self):
+        class Model(models.Model):
+            field = models.CharField(max_length=10, validators=[True])
+
+        field = Model._meta.get_field('field')
+        self.assertEqual(field.check(), [
+            Error(
+                "All 'validators' must be callable.",
+                hint=(
+                    "validators[0] (True) isn't a function or instance of a "
+                    "validator class."
+                ),
+                obj=field,
+                id='fields.E008',
+            ),
+        ])
+
     @unittest.skipUnless(connection.vendor == 'mysql',
                          "Test valid only for MySQL")
     def test_too_long_char_field_under_mysql(self):

tests/invalid_models_tests/test_relative_fields.py

@@ -102,7 +102,7 @@ class RelativeFieldTests(SimpleTestCase):
             m2m = models.ManyToManyField(
                 Model,
                 null=True,
-                validators=[''],
+                validators=[lambda x: x],
                 limit_choices_to={'name': 'test_name'},
                 through='ThroughModel',
                 through_fields=('modelm2m', 'model'),