old_contents: from distutils.core import Extension as _Extension
  from dist import _get_unpatched
  _Extension = _get_unpatched(_Extension)
  
  try:
      from Pyrex.Distutils.build_ext import build_ext
  except ImportError:
      have_pyrex = False
  else:
      have_pyrex = True
  
  
  class Extension(_Extension):
      """Extension that uses '.c' files in place of '.pyx' files"""
  
      if not have_pyrex:
          # convert .pyx extensions to .c 
          def __init__(self,*args,**kw):
              _Extension.__init__(self,*args,**kw)
              sources = []
              for s in self.sources:
                  if s.endswith('.pyx'):
                      sources.append(s[:-3]+'c')
                  else:
                      sources.append(s)
              self.sources = sources
  
  class Library(Extension):
      """Just like a regular Extension, but built as a library instead"""
  
  import sys, distutils.core, distutils.extension
  distutils.core.Extension = Extension
  distutils.extension.Extension = Extension
  if 'distutils.command.build_ext' in sys.modules:
      sys.modules['distutils.command.build_ext'].Extension = Extension
  
  
new_contents: from distutils.core import Extension as _Extension
  from setuptools.dist import _get_unpatched
  _Extension = _get_unpatched(_Extension)
  
  try:
      from Pyrex.Distutils.build_ext import build_ext
  except ImportError:
      have_pyrex = False
  else:
      have_pyrex = True
  
  
  class Extension(_Extension):
      """Extension that uses '.c' files in place of '.pyx' files"""
  
      if not have_pyrex:
          # convert .pyx extensions to .c 
          def __init__(self,*args,**kw):
              _Extension.__init__(self,*args,**kw)
              sources = []
              for s in self.sources:
                  if s.endswith('.pyx'):
                      sources.append(s[:-3]+'c')
                  else:
                      sources.append(s)
              self.sources = sources
  
  class Library(Extension):
      """Just like a regular Extension, but built as a library instead"""
  
  import sys, distutils.core, distutils.extension
  distutils.core.Extension = Extension
  distutils.extension.Extension = Extension
  if 'distutils.command.build_ext' in sys.modules:
      sys.modules['distutils.command.build_ext'].Extension = Extension
  
  
subject: Fix import that was breaking py3k