Fix ignore pymemcache's get_many returns False value

In some case, pymemcache returns {'key': False}
if client does not found.

It raises exception at Django-Cachalot.

Django-Cachalot's author said get_many should not contain a key
that's not in the cache, as stated in Django.

So we try to imprements get_many method and ignore if False
were included.

Author: heavenshell

django_elastipymemcache/client.py

@@ -2,4 +2,10 @@
 
 
 class Client(HashClient):
-    pass
+    def get_many(self, keys, gets=False, *args, **kwargs):
+        # pymemcache's HashClient may returns {'key': False}
+        end = super(Client, self).get_many(keys, gets, args, kwargs)
+
+        return {key: end[key] for key in end if end[key]}
+
+    get_multi = get_many

tests/test_backend.py

@@ -99,3 +99,49 @@ def test_invalidate_cache(get_cluster_info):
         pass
     eq_(backend._cache.get.call_count, 2)
     eq_(get_cluster_info.call_count, 3)
+
+
+@patch('django.conf.settings', global_settings)
+@patch('django_elastipymemcache.memcached.get_cluster_info')
+def test_client_get_many(get_cluster_info):
+    from django_elastipymemcache.memcached import ElastiPyMemCache
+
+    servers = [('h1', 0), ('h2', 0)]
+    get_cluster_info.return_value = {
+        'nodes': servers
+    }
+
+    backend = ElastiPyMemCache('h:0', {})
+    ret = backend.get_many(['key1'])
+    eq_(ret, {})
+
+    # When server does not found...
+    with patch('pymemcache.client.hash.HashClient._get_client') as p:
+        p.return_value = None
+        ret = backend.get_many(['key2'])
+        eq_(ret, {})
+
+    with patch('django_elastipymemcache.client.Client.get_many'):
+        with patch('pymemcache.client.hash.HashClient._safely_run_func') as p2:
+            p2.return_value = {
+                ':1:key3': 1509111630.048594
+            }
+
+            ret = backend.get_many(['key3'])
+            eq_(ret, {'key3': 1509111630.048594})
+
+    # If False value is included, ignore it.
+    with patch('pymemcache.client.hash.HashClient.get_many') as p:
+        p.return_value = {
+            ':1:key1': 1509111630.048594,
+            ':1:key2': False,
+            ':1:key3': 1509111630.058594,
+        }
+        ret = backend.get_many(['key1', 'key2', 'key3'])
+        eq_(
+            ret,
+            {
+                'key1': 1509111630.048594,
+                'key3': 1509111630.058594
+            },
+        )