Merge ~cjwatson/launchpad:six-iter-avoid-pyupgrade into launchpad:master

[Colin Watson]

Adjust ObjectSet.__iter__ to avoid pyupgrade confusion

pyupgrade rewrites `six.itervalues(dct)` as `dct.values()`, which is usually correct, but not when returned from an `__iter__` method. That must return an actual iterator, and returning a view object instead raises an exception:

  TypeError: iter() returned non-iterator of type 'dict_values'

Fixing this in pyupgrade seems to be hard as the AST walk doesn't have enough information about ancestor nodes beyond the immediate parent, so just manually fix the one place in Launchpad where this is a problem so that pyupgrade can handle other instances of this pattern mechanically.

[Ioana Lasc (ilasc)]

review: Approve

diff --git a/lib/lp/codehosting/inmemory.py b/lib/lp/codehosting/inmemory.py
index 522f9d1..5835dc1 100644
--- a/lib/lp/codehosting/inmemory.py
+++ b/lib/lp/codehosting/inmemory.py
@@ -130,7 +130,7 @@ class ObjectSet:
         del self._objects[db_object.id]
 
     def __iter__(self):
-        return six.itervalues(self._objects)
+        return iter(self._objects.values())
 
     def _find(self, **kwargs):
         [(key, value)] = kwargs.items()