This fix, while preventing the Queue to crash, does not give any way to  programatically detect that the message was dropped. This is a problem as we can no longer assume that the Queue will not drop messages. For instance, we can no longer detect deadlocks in concurrent.futures.ProcessPoolExecutor as done in https://github.com/python/cpython/pull/1013 where the crashed QueueFeederThread was used to monitor the working state of the executor.

We could either:
- Put a flag highlighting the fact that some messages where dropped.
- Add an argument to the Queue to close on pickling errors.

I'd be happy to work on a PR to implement any solution that you think is reasonable.