setup_requires with Cython?

Starting from 18.0 release of setuptools (released on 2015-06-23) it is possible to specify Cython in setup_requires and pass *.pyx modules sources for regular setuptools.Extension:

from setuptools import setup, Extension

setup(
    # ...
    setup_requires=[
        # Setuptools 18.0 properly handles Cython extensions.
        'setuptools>=18.0',
        'cython',
    ],
    ext_modules=[
        Extension(
            'mylib',
            sources=['src/mylib.pyx'],
        ),
    ],
)