'Pluggable version of get_command_class()'

def get_command_class(self, command):

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