[2.0.x] Fixed #27979 -- Made MySQL raise IntegrityError rather than OperationalError when saving negative numbers in PositiveInteger fields.

Backport of dd82f33271 from master

django/db/backends/mysql/base.py

@@ -57,7 +57,10 @@ class CursorWrapper:
     Implemented as a wrapper, rather than a subclass, so that it isn't stuck
     to the particular underlying representation returned by Connection.cursor().
     """
-    codes_for_integrityerror = (1048,)
+    codes_for_integrityerror = (
+        1048,  # Column cannot be null
+        1690,  # BIGINT UNSIGNED value is out of range
+    )
 
     def __init__(self, cursor):
         self.cursor = cursor

tests/model_fields/test_integerfield.py

@@ -1,6 +1,8 @@
+import unittest
+
 from django.core import validators
 from django.core.exceptions import ValidationError
-from django.db import connection, models
+from django.db import IntegrityError, connection, models
 from django.test import SimpleTestCase, TestCase
 
 from .models import (
@@ -151,6 +153,13 @@ class PositiveIntegerFieldTests(IntegerFieldTests):
     model = PositiveIntegerModel
     documented_range = (0, 2147483647)
 
+    @unittest.skipIf(connection.vendor == 'sqlite', "SQLite doesn't have a constraint.")
+    def test_negative_values(self):
+        p = PositiveIntegerModel.objects.create(value=0)
+        p.value = models.F('value') - 1
+        with self.assertRaises(IntegrityError):
+            p.save()
+
 
 class ValidationTests(SimpleTestCase):