- getgroups always fails.
- geteuid and getegid always return 0 (root), which confuse tarfile and
tests.
- hardlinks (link, linkat) always fails.
- non-encodable file names are not supported by NODERAWFS layer.
- mark more tests with dependency on subprocess and multiprocessing.
Mocking does not work if the module fails to import.
Ensure that directory file descriptors refer to directories different
from the current directory, and that src_dir_fd and dst_dir_fd refer
to different directories.
Add context manager open_dir_fd() in test.support.os_helper.
Currently we freeze several modules into the runtime. For each of these modules it is essential to bootstrapping the runtime that they be frozen. Any other stdlib module that we later freeze into the runtime is not essential. We can just as well import from the .py file. This PR lets users explicitly choose which should be used, with the new "-X frozen_modules=[on|off]" CLI flag. The default is "off" for now.
https://bugs.python.org/issue45020
