use customized constance (#4191)

thirdpart/constance/backends/__init__.py

@@ -0,0 +1,26 @@
+"""
+Defines the base constance backend
+"""
+
+
+class Backend(object):
+
+    def get(self, key):
+        """
+        Get the key from the backend store and return the value.
+        Return None if not found.
+        """
+        raise NotImplementedError
+
+    def mget(self, keys):
+        """
+        Get the keys from the backend store and return a list of the values.
+        Return an empty list if not found.
+        """
+        raise NotImplementedError
+
+    def set(self, key, value):
+        """
+        Add the value to the backend store given the key.
+        """
+        raise NotImplementedError