Pluggable version of get_command_class()

def get_command_class(self, command):
        """Pluggable version of get_command_class()"""
        if command in self.cmdclass:
            return self.cmdclass[command]

        eps = pkg_resources.iter_entry_points('distutils.commands', command)
        for ep in eps:
            ep.require(installer=self.fetch_build_egg)
            self.cmdclass[command] = cmdclass = ep.load()
            return cmdclass
        else:
            return _Distribution.get_command_class(self, command)