From 48888a1a67db0404e5a31c9ca0349984e496f26f Mon Sep 17 00:00:00 2001
From: Andrew Artajos <andrew.artajos.dev@gmail.com>
Date: Thu, 8 Oct 2015 17:05:01 +1100
Subject: [PATCH] Fixed #25501 -- Made the file-based cache backend use the
 highest pickling protocol.

---
 django/core/cache/backends/filebased.py | 4 ++--
 docs/releases/1.10.txt                  | 2 +-
 tests/cache/tests.py                    | 9 +++++++++
 3 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/django/core/cache/backends/filebased.py b/django/core/cache/backends/filebased.py
index c35efce92c..88a8b528b5 100644
--- a/django/core/cache/backends/filebased.py
+++ b/django/core/cache/backends/filebased.py
@@ -54,8 +54,8 @@ class FileBasedCache(BaseCache):
         try:
             with io.open(fd, 'wb') as f:
                 expiry = self.get_backend_timeout(timeout)
-                f.write(pickle.dumps(expiry, -1))
-                f.write(zlib.compress(pickle.dumps(value), -1))
+                f.write(pickle.dumps(expiry, pickle.HIGHEST_PROTOCOL))
+                f.write(zlib.compress(pickle.dumps(value, pickle.HIGHEST_PROTOCOL), -1))
             file_move_safe(tmp_path, fname, allow_overwrite=True)
             renamed = True
         finally:
diff --git a/docs/releases/1.10.txt b/docs/releases/1.10.txt
index 1087c0bb55..46cc18f467 100644
--- a/docs/releases/1.10.txt
+++ b/docs/releases/1.10.txt
@@ -106,7 +106,7 @@ Minor features
 Cache
 ^^^^^
 
-* ...
+* The file-based cache backend now uses the highest pickling protocol.
 
 CSRF
 ^^^^
diff --git a/tests/cache/tests.py b/tests/cache/tests.py
index dca08ee081..e77cec9151 100644
--- a/tests/cache/tests.py
+++ b/tests/cache/tests.py
@@ -65,6 +65,11 @@ class Unpickable(object):
         raise pickle.PickleError()
 
 
+class UnpicklableType(object):
+    # Unpicklable using the default pickling protocol on Python 2.
+    __slots__ = 'a',
+
+
 @override_settings(CACHES={
     'default': {
         'BACKEND': 'django.core.cache.backends.dummy.DummyCache',
@@ -1221,6 +1226,10 @@ class FileBasedCacheTests(BaseCacheTests, TestCase):
         cache.set('foo', 'bar')
         os.path.exists(self.dirname)
 
+    def test_cache_write_unpickable_type(self):
+        # This fails if not using the highest pickling protocol on Python 2.
+        cache.set('unpickable', UnpicklableType())
+
 
 @override_settings(CACHES={
     'default': {