Fix ConflictResolution tests

Python 3 really wants rich comparison operators

src/ZODB/ConflictResolution.py

@@ -183,13 +183,32 @@ class PersistentReference(object):
                 "can't reliably compare against different "
                 "PersistentReferences")
 
+    # Python 3 dropped __cmp__
+
+    def __eq__(self, other):
+        return self.__cmp__(other) == 0
+
+    def __ne__(self, other):
+        return self.__cmp__(other) != 0
+
+    def __lt__(self, other):
+        return self.__cmp__(other) < 0
+
+    def __gt__(self, other):
+        return self.__cmp__(other) > 0
+
+    def __le__(self, other):
+        return self.__cmp__(other) <= 0
+
+    def __ge__(self, other):
+        return self.__cmp__(other) >= 0
+
     def __repr__(self):
         return "PR(%s %s)" % (id(self), self.data)
 
     def __getstate__(self):
         raise PicklingError("Can't pickle PersistentReference")
 
-
     @property
     def klass(self):
         # for tests

src/ZODB/ConflictResolution.txt

@@ -66,9 +66,11 @@ use:
             class PCounter(Persistent):
                 '`value` is readonly; increment it with `inc`.'
 
+                # Fool BTree checks for sane comparison :/
                 def __cmp__(self, other):
-                    'Fool BTree checks for sane comparison :/'
                     return object.__cmp__(self, other)
+                def __lt__(self, other):
+                    return object.__lt__(self, other)
 
                 _val = 0
                 def inc(self):