[Cython] Language stability

[Stefan Behnel]

Hi,

Dag Sverre Seljebotn wrote:
> I think "from __future__ import division" is an excellent example of 
> supporting multiple language levels in a nice way, it is not that 
> horrible to do.

BTW, I actually think we need to support that anyway if we want to compile
Python code. Things like

 >>> from __future__ import unicode_literals
 >>> from __future__ import print_function

provide a simple upgrade path for Py3 syntax support. Both would just be
enabled for plain Python code (.py) when the compiler runs in a Py3 environment.

Now that you mention it, maybe changes in Cython and Pyrex could be enabled by

 >>> from __future__ cimport some_new_pyrex_syntax_feature

(mind the "cimport") ? We would then still need a roadmap for a versioned
upgrade path if we add a syntax change.

Stefan