Use setuptools.dist.Distribution instead of BuildExtCommand

setup.py

@@ -22,9 +22,10 @@ email: gsell.matthias@gmail.com
 date: 03-01-2020
 """
 
-from distutils.command.build_ext import build_ext
-from distutils.core import setup
-from distutils.extension import Extension
+from setuptools import Extension, dist, setup
+
+# install numpy before main is called
+dist.Distribution().fetch_build_eggs(['numpy~=1.18'])
 
 MAJOR_VERSION = 1
 MINOR_VERSION = 1
@@ -34,6 +35,8 @@ VERSION = '{}.{}.{}'.format(MAJOR_VERSION, MINOR_VERSION, PATCH_LEVEL)
 
 
 def main():
+    import numpy
+
     macros = [('MAJOR_VERSION', str(MAJOR_VERSION)),
               ('MINOR_VERSION', str(MINOR_VERSION)),
               ('PATCH_LEVEL', str(PATCH_LEVEL)),
@@ -46,18 +49,21 @@ def main():
     mshread_ext = Extension('mshread',
                             sources=['src/mshread.c'],
                             define_macros=macros,
+                            include_dirs=[numpy.get_include()],
                             extra_compile_args=compile_args,
                             extra_link_args=link_args)
 
     mshwrite_ext = Extension('mshwrite',
                              sources=['src/mshwrite.c'],
                              define_macros=macros,
+                             include_dirs=[numpy.get_include()],
                              extra_compile_args=compile_args,
                              extra_link_args=link_args)
 
     mshutils_ext = Extension('mshutils',
                              sources=['src/mshutils.c'],
                              define_macros=macros,
+                             include_dirs=[numpy.get_include()],
                              extra_compile_args=compile_args,
                              extra_link_args=link_args)
 
@@ -68,23 +74,10 @@ def main():
           author_email="gsell.matthias@gmail.com",
           ext_package='carputils.mshext',
           ext_modules=[mshread_ext, mshwrite_ext, mshutils_ext],
-          cmdclass={'build_ext': BuildExtCommand},
           install_requires=[
             'numpy'
           ])
 
 
-class BuildExtCommand(build_ext):
-
-    '''
-    Custom BuildExtCommand to include numpy only at build time
-    see also: https://stackoverflow.com/a/54717012
-    '''
-    def run(self):
-        import numpy
-        self.include_dirs.append(numpy.get_include())
-        build_ext.run(self)
-
-
 if __name__ == '__main__':
     main()