As mentioned in issue7060, weak dict iterators are easily broken by
cyclic garbage collection changing the size of the underlying dict storage:

  File "/home/rdmurray/python/py3k/Lib/weakref.py", line 121, in items
    for wr in self.data.values():
RuntimeError: dictionary changed size during iteration

One possible solution is to delay all removals until all iterators are
done. Here is a context manager-based solution.

> delay all removals until all iterators are done

+1

This new patch makes it possible to mutate the dict without messing with
the delayed removal when an iterator exists.

It occurs weaksets have the same problem, here is a new patch fixing
them as well.

LGTM

Committed in r77365 (py3k) and r77366 (3.1). Thank you.

The issue still exists in 2.6 and 2.7.

Closing issue 839159 as a duplicate of this one.

Any plans on actually patching this in 2.7 any time soon?  This is affecting our software and hanging it on random occasions.