Fixed #23650 -- Prevented migrate from calling checks 3 times

Thanks Ilya Baryshev for the report and Tim Graham for the review.

django/core/management/commands/migrate.py

@@ -165,6 +165,7 @@ class Command(BaseCommand):
                 database=db,
                 reset_sequences=False,
                 inhibit_post_migrate=True,
+                skip_checks=True,
             )
 
         # Migrate!

tests/migrations/test_commands.py

@@ -139,6 +139,27 @@ class MigrateTests(MigrationTestBase):
         stdout = six.StringIO()
         call_command("migrate", "migrated_unapplied_app", stdout=stdout)
 
+    @override_system_checks([])
+    @override_settings(MIGRATION_MODULES={"migrations": "migrations.test_migrations"})
+    def test_migrate_system_checks(self):
+        """
+        Migrate should only call system checks once, even with test_flush=True (Refs #23650).
+        """
+        from django.core.management.base import BaseCommand
+
+        self.counter = 0
+
+        def patched_check(self_, **kwargs):
+            self.counter = self.counter + 1
+
+        saved_check = BaseCommand.check
+        BaseCommand.check = patched_check
+        try:
+            call_command("migrate", "migrations", verbosity=0, test_flush=True)
+        finally:
+            BaseCommand.check = saved_check
+        self.assertEqual(self.counter, 1)
+
 
 class MakeMigrationsTests(MigrationTestBase):
     """