Add pycadf + fix oslo.messaging requirement

Pycadf pulls in an older version of oslo.messaging, as
does most of the other packages. Since 1.3.0 is released
and we are building it allow the dependency resolver/adjuster
to correctly adjust those packages to use the specified
version instead of the one found in the requirements files.

Change-Id: I59b607839a8b65274a08a4903cafb98ab8900870

anvil/decorators.py

@@ -0,0 +1,81 @@
+#    Copyright (C) 2014 Yahoo! Inc. All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+import time
+
+# Various useful decorators...
+
+#
+# Copyright 2011 Christopher Arndt, MIT License
+#
+# https://wiki.python.org/moin/PythonDecoratorLibrary#Cached_Properties
+
+
+# pylint: disable=C0103
+class cached_property(object):
+    '''Decorator for read-only properties evaluated only once within TTL period.
+
+    It can be used to created a cached property like this::
+
+        import random
+
+        # the class containing the property must be a new-style class
+        class MyClass(object):
+            # create property whose value is cached for ten minutes
+            @cached_property(ttl=600)
+            def randint(self):
+                # will only be evaluated every 10 min. at maximum.
+                return random.randint(0, 100)
+
+    The value is cached  in the '_cache' attribute of the object instance that
+    has the property getter method wrapped by this decorator. The '_cache'
+    attribute value is a dictionary which has a key for every property of the
+    object which is wrapped by this decorator. Each entry in the cache is
+    created only when the property is accessed for the first time and is a
+    two-element tuple with the last computed property value and the last time
+    it was updated in seconds since the epoch.
+
+    The default time-to-live (TTL) is 300 seconds (5 minutes). Set the TTL to
+    zero for the cached value to never expire.
+
+    To expire a cached property value manually just do::
+
+        del instance._cache[<property name>]
+
+    '''
+    def __init__(self, ttl=300):
+        self.ttl = ttl
+        self.fget = None
+
+    def __call__(self, fget, doc=None):
+        self.fget = fget
+        self.__doc__ = doc or fget.__doc__  # pylint: disable=W0201
+        self.__name__ = fget.__name__  # pylint: disable=W0201
+        self.__module__ = fget.__module__  # pylint: disable=W0201
+        return self
+
+    def __get__(self, inst, owner):
+        now = time.time()
+        try:
+            value, last_update = inst._cache[self.__name__]
+            if self.ttl > 0 and now - last_update > self.ttl:
+                raise AttributeError
+        except (KeyError, AttributeError):
+            value = self.fget(inst)
+            try:
+                cache = inst._cache
+            except AttributeError:
+                cache = inst._cache = {}
+            cache[self.__name__] = (value, now)
+        return value