Avoid assertion failures in deinitializers

[tristanlabelle]

There may be cases where a clean deinitialization is impossible. We should not assert in the deinit because it will always force the program to terminate in debug builds. Rather swallow errors and provide a way to handle them before deinit.

[z2oh]

What happens when an error is unhandled in a deinit? I tried googling but couldn't find a good answer

[tristanlabelle]

@z2oh I think a deinit simply cannot be throws, so you have to handle your errors like with any other non-throws function.