old_contents: from distutils.core import setup
  from Cython.Build import cythonize
  
  setup(
      name = "frozen_dict",
      ext_modules = cythonize("frozen_dict.pyx")
  )
new_contents: from distutils.core import setup
  from Cython.Build import cythonize
  
  from distutils.core import setup
  from distutils.extension import Extension
  
  if 3/2 == 1.5:
      version = 3
  else:
      version = 2
  
  if version == 3:
      setup(
          ext_modules = [Extension('frozen_dict', ['frozen_dict_py3.c'])]
      )
  else:
      setup(
          ext_modules = [Extension('frozen_dict', ['frozen_dict_py2.c'])]
      )
  
subject: Update setup.py