Fixed #26135 -- Adjusted the migration questioner's handling of disabled apps.

This was causing an issue when calling the `migrate` command in a test case with
the `available_apps` attribute pointing to an application with migrations
disabled using the `MIGRATION_MODULES` setting.

Thanks to Tim Graham for the review.

Refs #24919

3 files changed, 22 insertions, 0 deletions

diff --git a/django/db/migrations/questioner.py b/django/db/migrations/questioner.py
index aef80f4a52..47d4cdf130 100644
--- a/django/db/migrations/questioner.py
+++ b/django/db/migrations/questioner.py
@@ -38,6 +38,9 @@ class MigrationQuestioner(object):
         except LookupError:         # It's a fake app.
             return self.defaults.get("ask_initial", False)
         migrations_import_path = MigrationLoader.migrations_module(app_config.label)
+        if migrations_import_path is None:
+            # It's an application with migrations disabled.
+            return self.defaults.get("ask_initial", False)
         try:
             migrations_module = importlib.import_module(migrations_import_path)
         except ImportError:
diff --git a/docs/releases/1.9.2.txt b/docs/releases/1.9.2.txt
index e64c62e3da..1612a938a2 100644
--- a/docs/releases/1.9.2.txt
+++ b/docs/releases/1.9.2.txt
@@ -71,3 +71,7 @@ Bugfixes
 
 * Fixed a crash when using a reverse ``OneToOneField`` in
   ``ModelAdmin.readonly_fields`` (:ticket:`26060`).
+
+* Fixed a crash when calling the ``migrate`` command in a test case with the
+  ``available_apps`` attribute pointing to an application with migrations
+  disabled using the ``MIGRATION_MODULES`` setting (:ticket:`26135`).
diff --git a/tests/migrations/test_questioner.py b/tests/migrations/test_questioner.py
new file mode 100644
index 0000000000..d5ba18a684
--- /dev/null
+++ b/tests/migrations/test_questioner.py
@@ -0,0 +1,15 @@
+from __future__ import unicode_literals
+
+from django.db.migrations.questioner import MigrationQuestioner
+from django.test import SimpleTestCase
+from django.test.utils import override_settings
+
+
+class QuestionerTests(SimpleTestCase):
+    @override_settings(
+        INSTALLED_APPS=['migrations'],
+        MIGRATION_MODULES={'migrations': None},
+    )
+    def test_ask_initial_with_disabled_migrations(self):
+        questioner = MigrationQuestioner()
+        self.assertIs(False, questioner.ask_initial('migrations'))