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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _build_one_legacy(self, req, tempd, python_tag=None):
 """Build one InstallRequirement using the "legacy" build process. Returns path to wheel if successfully built. Otherwise, returns None. """

        base_args = self._base_setup_args(req)

        spin_message = 'Building wheel for %s (setup.py)' % (req.name,)
        with open_spinner(spin_message) as spinner:
            logger.debug('Destination directory: %s', tempd)
            wheel_args = base_args + ['bdist_wheel', '-d', tempd] \
                + self.build_options

            if python_tag is not None:
                wheel_args += ["--python-tag", python_tag]

            try:
                output = call_subprocess(wheel_args, cwd=req.setup_py_dir,
                                         show_stdout=False, spinner=spinner)
            except Exception:
                spinner.finish("error")
                logger.error('Failed building wheel for %s', req.name)
                return None
            names = os.listdir(tempd)
            wheel_path = get_legacy_build_wheel_path(
                names=names,
                temp_dir=tempd,
                req=req,
                command_args=wheel_args,
                command_output=output,
            )
            return wheel_path