> If I understood PR 10919 correctly, sysconfig.get_config_var('userbase') can now return unexpanded paths containing '~'. Is it intended despite the previous discussion starting with msg135047?

With my PR 10919, "python3 setup.py install" and  "python3 setup.py install --user" still fail with:

Traceback (most recent call last):
  File "setup.py", line 79, in <module>
    main()
  File "setup.py", line 75, in main
    setup(**options)
  File "/tmp/cpython/Lib/distutils/core.py", line 121, in setup
    dist.parse_config_files()
  File "/tmp/cpython/Lib/distutils/dist.py", line 397, in parse_config_files
    filenames = self.find_config_files()
  File "/tmp/cpython/Lib/distutils/dist.py", line 349, in find_config_files
    check_environ()
  File "/tmp/cpython/Lib/distutils/util.py", line 161, in check_environ
    os.environ['HOME'] = pwd.getpwuid(os.getuid())[5]
KeyError: 'getpwuid(): uid not found: 12345'

I suggest to open a new issue if you want to enhance the error message and/or handle getpwuid() failure in find_config_files().

I prefer to stick to the initial bug report which hasn't been fixed in 8 years:

> When Python cannot find the home directory of the user invoking it, it prints "'import site' failed; use -v for traceback".

IMHO PR 10919 fix is straighforward, it respects the contract (documentation) of posixpath.expanduser() ("If user or $HOME is unknown, do nothing."), and expanduser() already handles KeyError on getpwnam() (since the function has been created in 1992 by Guido van Rossum! commit 7ac4878773040158038031a85be122d9e7071afe).