[Culprit-Finder] Seperate gae related part in cache_decorator and gitile repository to gae_libs/

appengine/findit/lib/cache.py

+# Copyright 2016 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+
+class Cache(object):
+  """An interface to cache and retrieve data.
+
+  Subclasses should implement the Get/Set functions.
+  TODO: Add a Delete function (default to no-op) if needed later.
+  """
+  def Get(self, key):
+    """Returns the cached data for the given key if available.
+
+    Args:
+      key (str): The key to identify the cached data.
+    """
+    raise NotImplementedError()
+
+  def Set(self, key, data, expire_time=0):
+    """Cache the given data which is identified by the given key.
+
+    Args:
+      key (str): The key to identify the cached data.
+      data (object): The python object to be cached.
+      expire_time (int): Number of seconds from current time (up to 1 month).
+    """
+    raise NotImplementedError()