old_contents: #!/usr/bin/env python
  
  from distutils.core import setup
  from distutils.extension import Extension
  
  try:
      from Cython.Distutils import build_ext
      setup(
          name = 'mtbl',
          ext_modules = [ Extension('mtbl', ['mtbl.pyx'], libraries = ['mtbl']) ],
          cmdclass = {'build_ext': build_ext},
      )
  except ImportError:
      setup(
          name = 'mtbl',
          ext_modules = [ Extension('mtbl', ['mtbl.c'], libraries = ['mtbl']) ],
      )
  
new_contents: #!/usr/bin/env python
  
  NAME = 'pymtbl'
  VERSION = '0.2'
  
  from distutils.core import setup
  from distutils.extension import Extension
  import os
  
  try:
      from Cython.Distutils import build_ext
      setup(
          name = NAME,
          version = VERSION,
          ext_modules = [ Extension('mtbl', ['mtbl.pyx'], libraries = ['mtbl']) ],
          cmdclass = {'build_ext': build_ext},
      )
  except ImportError:
      if os.path.isfile('mtbl.c'):
          setup(
              name = NAME,
              version = VERSION,
              ext_modules = [ Extension('mtbl', ['mtbl.c'], libraries = ['mtbl']) ],
          )
      else:
          raise
  
subject: add NAME, VERSION, and only skip cython rebuild if mtbl.c is available