Fixed #21012 -- New API to access cache backends.

Thanks Curtis Malony and Florian Apolloner.

Squashed commit of the following:

commit 3380495e93f5e81b80a251b03ddb0a80b17685f5
Author: Aymeric Augustin <aymeric.augustin@m4x.org>
Date:   Sat Nov 23 14:18:07 2013 +0100

    Looked up the template_fragments cache at runtime.

commit 905a74f52b24a198f802520ff06290a94dedc687
Author: Aymeric Augustin <aymeric.augustin@m4x.org>
Date:   Sat Nov 23 14:19:48 2013 +0100

    Removed all uses of create_cache.

    Refactored the cache tests significantly.

    Made it safe to override the CACHES setting.

commit 35e289fe9285feffed3c60657af9279a6a2cfccc
Author: Aymeric Augustin <aymeric.augustin@m4x.org>
Date:   Sat Nov 23 12:23:57 2013 +0100

    Removed create_cache function.

commit 8e274f747a1f1c0c0e6c37873e29067f7fa022e8
Author: Aymeric Augustin <aymeric.augustin@m4x.org>
Date:   Sat Nov 23 12:04:52 2013 +0100

    Updated docs to describe a simplified cache backend API.

commit ee7eb0f73e6d4699edcf5d357dce715224525cf6
Author: Curtis Maloney <curtis@tinbrain.net>
Date:   Sat Oct 19 09:49:24 2013 +1100

    Fixed #21012 -- Thread-local caches, like databases.

1 files changed, 2 insertions, 12 deletions

diff --git a/django/core/cache/backends/memcached.py b/django/core/cache/backends/memcached.py
index c49c20e59b..216ceb04e1 100644
--- a/django/core/cache/backends/memcached.py
+++ b/django/core/cache/backends/memcached.py
@@ -2,13 +2,13 @@
 
 import time
 import pickle
-from threading import local
 
 from django.core.cache.backends.base import BaseCache, DEFAULT_TIMEOUT
 
 from django.utils import six
 from django.utils.deprecation import RenameMethodsBase
 from django.utils.encoding import force_str
+from django.utils.functional import cached_property
 
 
 class BaseMemcachedCacheMethods(RenameMethodsBase):
@@ -177,24 +177,14 @@ class PyLibMCCache(BaseMemcachedCache):
     "An implementation of a cache binding using pylibmc"
     def __init__(self, server, params):
         import pylibmc
-        self._local = local()
         super(PyLibMCCache, self).__init__(server, params,
                                            library=pylibmc,
                                            value_not_found_exception=pylibmc.NotFound)
 
-    @property
+    @cached_property
     def _cache(self):
-        # PylibMC uses cache options as the 'behaviors' attribute.
-        # It also needs to use threadlocals, because some versions of
-        # PylibMC don't play well with the GIL.
-        client = getattr(self._local, 'client', None)
-        if client:
-            return client
-
         client = self._lib.Client(self._servers)
         if self._options:
             client.behaviors = self._options
 
-        self._local.client = client
-
         return client