Best ways to debug setuptools/pip?

[AndrewAnnex]

related to my issue #2818, I am trying to provide more helpful information for the issue but I am having trouble getting debuggers to work with setuptools pep517/518. Adding breakpoint() to my custom build commands (via cmdclass) just results in NameError: name 'breakpoint' is not defined when running pip install dist/*.tar/gz. Are there other ways to ensure I get a stack traceback with setuptools/pip? I have went as far as editing the source files in site-packages for setuptools to include breakpoints aswell but no success so far, pip just returns unhelpful traceback:

Traceback (most recent call last):
  File "/home/andrew/anaconda3/envs/spiceypydev/lib/python3.9/site-packages/pip/_internal/cli/base_command.py", line 164, in exc_logging_wrapper
    status = run_func(*args)
  File "/home/andrew/anaconda3/envs/spiceypydev/lib/python3.9/site-packages/pip/_internal/cli/req_command.py", line 204, in wrapper
    return func(self, options, args)
  File "/home/andrew/anaconda3/envs/spiceypydev/lib/python3.9/site-packages/pip/_internal/commands/install.py", line 374, in run
    raise InstallationError(