Better identification of broken Distribution objects

Currently, I'm getting an error on Python 3.8 and 3.9 in https://github.com/pypa/build/pull/820:

docker run --rm -it python:3.9 bash
pip install tox
git clone https://github.com/pypa/build
cd build
tox -e py39 -- -k test_metadata_path_no_prepare -v

...
File "/build/.tox/py39/lib/python3.9/site-packages/importlib_metadata/compat/py39.py", line 23, in normalized_name
    return Prepared.normalize(getattr(dist, "name", None) or dist.metadata['Name'])
  File "/build/.tox/py39/lib/python3.9/site-packages/importlib_metadata/__init__.py", line 889, in normalize
    return re.sub(r"[-_.]+", "-", name).lower().replace('-', '_')
  File "/usr/local/lib/python3.9/re.py", line 210, in sub
    return _compile(pattern, flags).sub(repl, string, count)
TypeError: expected string or bytes-like object

The problem is dist.__dict__={'_path': PosixPath('/build/tests/packages/test-no-prepare/test_no_prepare.egg-info')}. I think this is tripping up on tests/packages/test-no-prepare/test_no_prepare.egg-info/ and the local backend. But I don't know what updated to cause this to start happening.

Regardless of the solution, though, I think the handling here for a missing name should be better, there wasn't any useful info in the error message to tell me about the dist that was failing. I had to add print(f"{dist.__dict__=}") to see it. Or maybe the normalize name could return None, and let the failure happen elsewhere.

Beginne damit, den Fehler mit den im Issue angegebenen Python 3.9-Docker- und tox-Befehlen zu reproduzieren, und lies dann normalized_name in importlib_metadata/compat/py39.py sowie normalize in importlib_metadata/init.py. Verfolge, wie die Distribution, die nur _path enthält, die Namensnormalisierung erreicht; die Arbeit ist abgeschlossen, wenn ein fehlender oder ungültiger Name eine nützliche Identifizierung der fehlschlagenden Distribution liefert und die relevanten Tests bestehen.