Update test_memcached.py (bbangert#228)

Fix CI per bbangert#227 (comment)

Author: jonathanspw

tests/test_memcached.py

@@ -291,9 +291,9 @@ def test_uses_pylibmc_client(self):
 
     def test_dont_use_pylibmc_client(self):
         from beaker.ext.memcached import _load_client
-        load_mock = mock.Mock()
+        load_mock = unittest.mock.Mock()
         load_mock.return_value = _load_client('memcache')
-        with mock.patch('beaker.ext.memcached._load_client', load_mock):
+        with unittest.mock.patch('beaker.ext.memcached._load_client', load_mock):
             cache = Cache('test', data_dir='./cache', url=mc_url, type="ext:memcached")
             assert not isinstance(cache.namespace, memcached.PyLibMCNamespaceManager)
             assert isinstance(cache.namespace, memcached.MemcachedNamespaceManager)