[Cython] Cython 0.26 release

[Robert Bradshaw]

On Wed, Jun 21, 2017 at 5:29 AM, Jeroen Demeyer <jdemeyer at cage.ugent.be> wrote:
> Could the error from
> https://github.com/cython/cython/issues/1732
> at
> https://github.com/cython/cython/blob/master/Cython/Compiler/Symtab.py#L2099
> be a warning instead?
>
> SageMath has quite a bit of code hitting this error. It would make our life
> easier if we could fix it gradually instead of being forced to fix it all
> before upgrading to Cython 0.26.

Could you give some examples? Is it cdef->cpdef, or something else?
It's possible that the error needs to be made narrower, but I'd really
like to avoid incorrect code that could lead to wrong methods being
called.