[brisbane-core:MERGE] Some cleanups around tree.iter_changes

[John Arbash Meinel]

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Vincent Ladeuil wrote:
> This patch provides a proper InterTree object for trees that both use
> CHKInventories.
> 
> Feedback welcome on the test parametrization in particular,
> 
>          Vincent
> 
> 

+    def is_compatible(source, target):
+        if (isinstance(source, RevisionTree)
+            and isinstance(target, RevisionTree)):
+            try:
+                # Only CHK inventories have id_to_entry attribute
+                source.inventory.id_to_entry
+                target.inventory.id_to_entry
+                return True
+            except AttributeError:
+                pass
+        return False

^- I think this is better written as:

if (getattr(source.inventory, 'id_to_entry', None) is not None
    and getattr(target.inventory, 'id_to_entry', None) is not None):
  return True
return False

BB:tweak

John
=:->
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