old_contents: import setuptools
  from setuptools.extension import Extension
  
  class custom_wrapper(object):
      def __new__(cls, *args, **kwargs):
          from setuptools.command.build_ext import build_ext
          class custom_build_ext(build_ext, object):
              def run(self):
                  import numpy as np
                  self.include_dirs.append(np.get_include())
                  build_ext.run(self)
          return custom_build_ext(*args, **kwargs)
  
  extensions = [
      Extension(
          'keras_retinanet.utils.compute_overlap',
          ['keras_retinanet/utils/compute_overlap.pyx']
      ),
  ]
  
  setuptools.setup(
      name             = 'keras-retinanet',
      version          = '0.5.0',
      description      = 'Keras implementation of RetinaNet object detection.',
      url              = 'https://github.com/fizyr/keras-retinanet',
      author           = 'Hans Gaiser',
      author_email     = 'h.gaiser@fizyr.com',
      maintainer       = 'Hans Gaiser',
      maintainer_email = 'h.gaiser@fizyr.com',
      cmdclass         = {'build_ext': custom_wrapper},
      packages         = setuptools.find_packages(),
      install_requires = ['keras', 'keras-resnet', 'six', 'scipy', 'cython', 'Pillow', 'opencv-python', 'progressbar2'],
      entry_points     = {
          'console_scripts': [
              'retinanet-train=keras_retinanet.bin.train:main',
              'retinanet-evaluate=keras_retinanet.bin.evaluate:main',
              'retinanet-debug=keras_retinanet.bin.debug:main',
              'retinanet-convert-model=keras_retinanet.bin.convert_model:main',
          ],
      },
      ext_modules    = extensions,
      setup_requires = ["cython>=0.28", "numpy>=1.14.0"]
  )
  
new_contents: import setuptools
  from setuptools.extension import Extension
  from distutils.command.build_ext import build_ext as DistUtilsBuildExt
  
  
  class BuildExtension(setuptools.Command):
      description     = DistUtilsBuildExt.description
      user_options    = DistUtilsBuildExt.user_options
      boolean_options = DistUtilsBuildExt.boolean_options
      help_options    = DistUtilsBuildExt.help_options
  
      def __init__(self, *args, **kwargs):
          from setuptools.command.build_ext import build_ext as SetupToolsBuildExt
  
          # Bypass __setatrr__ to avoid infinite recursion.
          self.__dict__['_command'] = SetupToolsBuildExt(*args, **kwargs)
  
      def __getattr__(self, name):
          return getattr(self._command, name)
  
      def __setattr__(self, name, value):
          setattr(self._command, name, value)
  
      def initialize_options(self, *args, **kwargs):
          return self._command.initialize_options(*args, **kwargs)
  
      def finalize_options(self, *args, **kwargs):
          ret = self._command.finalize_options(*args, **kwargs)
          import numpy
          self.include_dirs.append(numpy.get_include())
          return ret
  
      def run(self, *args, **kwargs):
          return self._command.run(*args, **kwargs)
  
  
  extensions = [
      Extension(
          'keras_retinanet.utils.compute_overlap',
          ['keras_retinanet/utils/compute_overlap.pyx']
      ),
  ]
  
  
  setuptools.setup(
      name             = 'keras-retinanet',
      version          = '0.5.0',
      description      = 'Keras implementation of RetinaNet object detection.',
      url              = 'https://github.com/fizyr/keras-retinanet',
      author           = 'Hans Gaiser',
      author_email     = 'h.gaiser@fizyr.com',
      maintainer       = 'Hans Gaiser',
      maintainer_email = 'h.gaiser@fizyr.com',
      cmdclass         = {'build_ext': BuildExtension},
      packages         = setuptools.find_packages(),
      install_requires = ['keras', 'keras-resnet', 'six', 'scipy', 'cython', 'Pillow', 'opencv-python', 'progressbar2'],
      entry_points     = {
          'console_scripts': [
              'retinanet-train=keras_retinanet.bin.train:main',
              'retinanet-evaluate=keras_retinanet.bin.evaluate:main',
              'retinanet-debug=keras_retinanet.bin.debug:main',
              'retinanet-convert-model=keras_retinanet.bin.convert_model:main',
          ],
      },
      ext_modules    = extensions,
      setup_requires = ["cython>=0.28", "numpy>=1.14.0"]
  )
  
subject: Update build_ext command in setup.py