Fix matthewwithanm#317 RemovedInDjango19Warning: 'get_cache'

Make a `get_cache` function in `utils` which will call
`django.core.cache.get_cache` if we are running Django < 1.7 or
will mimic it's behaviour for newer versions of Django

Author: vstoykov

imagekit/cachefiles/backends.py

@@ -1,7 +1,6 @@
-from ..utils import get_singleton, sanitize_cache_key
+from ..utils import get_singleton, get_cache, sanitize_cache_key
 import warnings
 from copy import copy
-from django.core.cache import get_cache
 from django.core.exceptions import ImproperlyConfigured
 
 

imagekit/utils.py

@@ -5,6 +5,7 @@
 from hashlib import md5
 
 from django.conf import settings
+from django.core import signals
 from django.core.exceptions import ImproperlyConfigured
 from django.core.files import File
 try:
@@ -151,6 +152,25 @@ def call_strategy_method(file, method_name):
         fn(file)
 
 
+def get_cache(backend, **kwargs):
+    """
+    Compatibilty wrapper for getting Django's cache backend instance
+    """
+    try:
+        from django.core.cache import _create_cache
+    except ImportError:
+        # Django < 1.7
+        from django.core.cache import get_cache as _get_cache
+        return _get_cache(backend, **kwargs)
+
+    cache = _create_cache(backend, **kwargs)
+    # Some caches -- python-memcached in particular -- need to do a cleanup at the
+    # end of a request cycle. If not implemented in a particular backend
+    # cache.close is a no-op
+    signals.request_finished.connect(cache.close)
+    return cache
+
+
 def sanitize_cache_key(key):
     if settings.IMAGEKIT_USE_MEMCACHED_SAFE_CACHE_KEY:
         # Memcached keys can't contain whitespace or control characters.