Pip: 回溯运行 setup.py clean: ModuleNotFoundError: No module named 'setuptools'

在问题 #6634 中报告说，在使用 (PEP 517) 构建轮子时，不需要setup.py clean失败时显示的回溯。

摘抄：

  Running `pyo3-pack build -i python --no-sdist --bindings=cffi`
  Error: Command '['pyo3-pack', 'build', '-i', 'python', '--no-sdist', '--bindings=cffi']' returned non-zero exit status 1.
  Building wheel for cffi-pure (PEP 517) ... error
  ERROR: Failed building wheel for cffi-pure
  Running setup.py clean for cffi-pure
  Running command /home/konsti/pyo3-pack/venv/bin/python -u -c 'import setuptools, tokenize;__file__='"'"'/tmp/pip-req-build-sphjswqi/setup.py'"'"';f=getattr(tokenize, '"'"'open'"'"', open)(__file__);code=f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' clean --all
  Traceback (most recent call last):
    File "<string>", line 1, in <module>
  ModuleNotFoundError: No module named 'setuptools'
  ERROR: Failed cleaning build dir for cffi-pure
Failed to build cffi-pure