Pip: ¿Deberíamos imprimir un error si --user y --target se usan juntos?

Si intento pasar ambos, obtengo un error de distutils. Está bastante claro, por lo que tal vez por eso no esté verificado en pip, pero tal vez todavía tenga sentido verificarlo y fallar más rápido.

$ pip install --user --target test-tgt/  astcheck
Collecting astcheck
  Using cached https://files.pythonhosted.org/packages/8d/a7/23752054ffc65eca77b2137f88c3b4b8d196112b5e13e9536f194ab67756/astcheck-0.2.5-py2.py3-none-any.whl
Installing collected packages: astcheck
Exception:
Traceback (most recent call last):
  File "/usr/lib/python3.7/site-packages/pip/_internal/cli/base_command.py", line 179, in main
    status = self.run(options, args)
  File "/usr/lib/python3.7/site-packages/pip/_internal/commands/install.py", line 421, in run
    strip_file_prefix=options.strip_file_prefix,
  File "/usr/lib/python3.7/site-packages/pip/_internal/req/__init__.py", line 57, in install_given_reqs
    **kwargs
  File "/usr/lib/python3.7/site-packages/pip/_internal/req/req_install.py", line 917, in install
    strip_file_prefix=strip_file_prefix,
  File "/usr/lib/python3.7/site-packages/pip/_internal/req/req_install.py", line 447, in move_wheel_files
    strip_file_prefix=strip_file_prefix,
  File "/usr/lib/python3.7/site-packages/pip/_internal/wheel.py", line 326, in move_wheel_files
    prefix=prefix,
  File "/usr/lib/python3.7/site-packages/pip/_internal/locations.py", line 180, in distutils_scheme
    i.finalize_options()
  File "/usr/lib64/python3.7/distutils/command/install.py", line 252, in finalize_options
    raise DistutilsOptionError("can't combine user with prefix, "
distutils.errors.DistutilsOptionError: can't combine user with prefix, exec_prefix/home, or install_(plat)base

Esto parece bastante sencillo, por lo que cambiar de estado.

@pradyunsg Estoy en eso. : +1: