On Jan 11, 2016, at 07:20 PM, Serhiy Storchaka wrote:

>I think we have to left this restriction in 3.6 (and Cython should fix its
>bug by providing either __getnewargs__/ __getnewargs_ex__, __getstate__ or
>__reduce__/__reduce_ex__). But in 2.7 and 3.5 we should allow current Cython
>to work (even obtaining wrong result) by removing the check at all or by
>making it emit only a warning.

I'm okay with reverting the change in 2.7 and 3.5 since those are clearly
regressions (whether or not Cython unpickles/copies correctly build failures
are regressions).

I'm also okay with leaving the restriction in 3.6, at least for now.  We can
let Cython upstream complain if they disagree with the location of the bug.

I will update the various branches.  Thanks for the good discussion!