Looks good to me as well.  I'll go ahead with applying the patch.

Berker:  I'm not sure it's worth adding something like `util.info("Serialization failure on: %r", msg)`.  If serialization failed for some reason other than MemoryError, we will be communicating the output of format_exc() back to the client.  If serialization failed due to a MemoryError (which has tripped up plenty of people) then our util.info may similarly fail.



Note that with the patch recently applied to issue6766, under 3.6 the second example no longer triggers an exception.  That second example can even continue:
    >>> ns_proxy.my_event_proxy.set()
    >>> ns_proxy.my_event_proxy.is_set()
    True
    >>> evt_proxy.is_set()
    True
    >>> evt_proxy.clear()
    >>> ns_proxy.my_event_proxy.is_set()
    False