Ensure User.last_login is nullable

aaa/migrations/0008_user_last_login_null.py

+# -*- coding: utf-8 -*-
+# ----------------------------------------------------------------------
+# Set auth_user.last_login to NULLable
+# ----------------------------------------------------------------------
+# Copyright (C) 2007-2019 The NOC Project
+# See LICENSE for details
+# ----------------------------------------------------------------------
+
+# NOC modules
+from noc.core.migration.base import BaseMigration
+
+
+class Migration(BaseMigration):
+    def migrate(self):
+        is_nullable = self.db.execute(
+            """
+            SELECT is_nullable = 'YES' 
+            FROM information_schema.columns 
+            WHERE 
+              table_name = 'auth_user'
+              AND column_name = 'last_login'
+            """
+        )[0][0]
+        if is_nullable:
+            return
+        self.db.execute(
+            """
+            ALTER TABLE auth_user
+            ALTER last_login
+            DROP NOT NULL
+            """
+        )