From 6a98396b9da56bf5eb1c94e037b844eb9bdd1a45 Mon Sep 17 00:00:00 2001
From: Caio Ariede <caio.ariede@gmail.com>
Date: Sun, 23 Aug 2015 21:07:00 -0300
Subject: [PATCH] Fixed #25246 -- Guarded against duplicate paths in AppConfig.

---
 django/apps/config.py | 4 ++++
 tests/apps/tests.py   | 8 ++++++++
 2 files changed, 12 insertions(+)

diff --git a/django/apps/config.py b/django/apps/config.py
index 98070e62c8..6a0c8d8e57 100644
--- a/django/apps/config.py
+++ b/django/apps/config.py
@@ -62,6 +62,10 @@ class AppConfig(object):
             filename = getattr(module, '__file__', None)
             if filename is not None:
                 paths = [os.path.dirname(filename)]
+            else:
+                # For unknown reasons, sometimes the list returned by __path__
+                # contains duplicates that must be removed (#25246).
+                paths = list(set(paths))
         if len(paths) > 1:
             raise ImproperlyConfigured(
                 "The app module %r has multiple filesystem locations (%r); "
diff --git a/tests/apps/tests.py b/tests/apps/tests.py
index ae8f0c6c92..9e34773a77 100644
--- a/tests/apps/tests.py
+++ b/tests/apps/tests.py
@@ -365,6 +365,14 @@ class AppConfigTests(SimpleTestCase):
         with self.assertRaises(ImproperlyConfigured):
             AppConfig('label', Stub(__path__=['a', 'b']))
 
+    def test_duplicate_dunder_path_no_dunder_file(self):
+        """
+        If the __path__ attr contains duplicate paths and there is no
+        __file__, they duplicates should be deduplicated (#25246).
+        """
+        ac = AppConfig('label', Stub(__path__=['a', 'a']))
+        self.assertEqual(ac.path, 'a')
+
 
 @skipUnless(six.PY3, "Namespace packages sans __init__.py were added in Python 3.3")
 class NamespacePackageAppTests(SimpleTestCase):