Use rich comparisons for Attribute and FieldAttribute

Because __cmp__ is not supported on Python 3.

lib/ansible/playbook/attribute.py

@@ -19,6 +19,7 @@
 from __future__ import (absolute_import, division, print_function)
 __metaclass__ = type
 
+
 class Attribute:
 
     def __init__(self, isa=None, private=False, default=None, required=False, listof=None, priority=0, always_post_validate=False):
@@ -31,8 +32,26 @@ class Attribute:
         self.priority = priority
         self.always_post_validate = always_post_validate
 
-    def __cmp__(self, other):
-       return cmp(other.priority, self.priority)
+    def __eq__(self, other):
+        return other.priority == self.priority
+
+    def __ne__(self, other):
+        return other.priority != self.priority
+
+    # NB: higher priority numbers sort first
+
+    def __lt__(self, other):
+        return other.priority < self.priority
+
+    def __gt__(self, other):
+        return other.priority > self.priority
+
+    def __le__(self, other):
+        return other.priority <= self.priority
+
+    def __ge__(self, other):
+        return other.priority >= self.priority
+
 
 class FieldAttribute(Attribute):
     pass