old_contents: import sys
  import re
  import functools
  import distutils.core
  import distutils.errors
  import distutils.extension
  
  from setuptools.extern.six.moves import map
  
  from .dist import _get_unpatched
  from . import msvc
  
  _Extension = _get_unpatched(distutils.core.Extension)
  
  msvc.patch_for_specialized_compiler()
  
  
  def _have_cython():
      """
      Return True if Cython can be imported.
      """
      cython_impl = 'Cython.Distutils.build_ext',
      try:
          # from (cython_impl) import build_ext
          __import__(cython_impl, fromlist=['build_ext']).build_ext
          return True
      except Exception:
          pass
      return False
  
  
  # for compatibility
  have_pyrex = _have_cython
  
  
  class Extension(_Extension):
      """Extension that uses '.c' files in place of '.pyx' files"""
  
      def _convert_pyx_sources_to_lang(self):
          """
          Replace sources with .pyx extensions to sources with the target
          language extension. This mechanism allows language authors to supply
          pre-converted sources but to prefer the .pyx sources.
          """
          if _have_cython():
              # the build has Cython, so allow it to compile the .pyx files
              return
          lang = self.language or ''
          target_ext = '.cpp' if lang.lower() == 'c++' else '.c'
          sub = functools.partial(re.sub, '.pyx$', target_ext)
          self.sources = list(map(sub, self.sources))
  
  
  class Library(Extension):
      """Just like a regular Extension, but built as a library instead"""
  
  
  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: import sys
  import re
  import functools
  import distutils.core
  import distutils.errors
  import distutils.extension
  
  from setuptools.extern.six.moves import map
  
  from .dist import _get_unpatched
  from . import msvc
  
  _Extension = _get_unpatched(distutils.core.Extension)
  
  msvc.patch_for_specialized_compiler()
  
  
  def _have_cython():
      """
      Return True if Cython can be imported.
      """
      cython_impl = 'Cython.Distutils.build_ext'
      try:
          # from (cython_impl) import build_ext
          __import__(cython_impl, fromlist=['build_ext']).build_ext
          return True
      except Exception:
          pass
      return False
  
  
  # for compatibility
  have_pyrex = _have_cython
  
  
  class Extension(_Extension):
      """Extension that uses '.c' files in place of '.pyx' files"""
  
      def _convert_pyx_sources_to_lang(self):
          """
          Replace sources with .pyx extensions to sources with the target
          language extension. This mechanism allows language authors to supply
          pre-converted sources but to prefer the .pyx sources.
          """
          if _have_cython():
              # the build has Cython, so allow it to compile the .pyx files
              return
          lang = self.language or ''
          target_ext = '.cpp' if lang.lower() == 'c++' else '.c'
          sub = functools.partial(re.sub, '.pyx$', target_ext)
          self.sources = list(map(sub, self.sources))
  
  
  class Library(Extension):
      """Just like a regular Extension, but built as a library instead"""
  
  
  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 _have_cython