Add __ne__ built-in function

In Python 3 __ne__ by default delegates to __eq__ and inverts the
result, but in Python 2 they urge you to define __ne__ when you
define __eq__ for it to work properly [1].There are no implied
relationships among the comparison operators. The truth of x==y
does not imply that x!=y is false. Accordingly, when defining __eq__(),
one should also define __ne__() so that the operators will behave
as expected.
[1]https://docs.python.org/2/reference/datamodel.html#object.__ne__

Change-Id: I05f4ecbdc9d430f970a11b0451a7699d06f8a8ad

solar/dblayer/lfu_cache.py

@@ -68,6 +68,9 @@ class LFUCache(object):
         else:
             return self == other
 
+    def __ne__(self, other):
+        return not self.__eq__(other)
+
     def __setitem__(self, item, value):
         self.set(item, value)
 

solar/dblayer/proxy.py

@@ -34,5 +34,8 @@ class DBLayerProxy(wrapt.ObjectProxy):
             return self.__wrapped__ == other
         return self.__wrapped__ == other.__wrapped__
 
+    def __ne__(self, other):
+        return not self.__eq__(other)
+
     def __repr__(self):
         return "<P: %r>" % self.__wrapped__

solar/dblayer/solar_models.py

@@ -1087,6 +1087,9 @@ class Task(Model):
             return self.key == other
         return self.key == other.key
 
+    def __ne__(self, other):
+        return not self.__eq__(other)
+
     def __repr__(self):
         return 'Task(execution={} name={})'.format(self.execution, self.name)