python: remove auto-generated pyproject.toml file

For reasons that at-present escape me, pipenv insists on creating a stub
pyproject.toml file. This file is a nuisance, because its mere presence
changes the behavior of various tools.

For instance, this stub file will cause "pip install --user -e ." to
fail in spectacular fashion with misleading errors. "pip install -e ."
works okay, but for some reason pip does not support editable installs
to the user directory when using PEP517.

References:
  pypa/pip#9990
  pypa/pip#7953

As outlined in ea1213b, it is still too early for us to consider
moving to a PEP-517 exclusive package. We must support older
distributions, so squash the annoyance for now. (Python 3.6 shipped Dec
2016, PEP517 support showed up in pip sometime in 2019 or so.)

Add 'pyproject.toml' to the 'make clean' target, and also delete it
after every pipenv invocation issued by the Makefile.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Willian Rampazzo <willianr@redhat.com>
Reviewed-by: Wainer dos Santos Moschetta <wainersm@redhat.com>
Message-id: 20210629214323.1329806-15-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>

python/Makefile

@@ -49,6 +49,7 @@ help:
 pipenv: .venv
 .venv: Pipfile.lock
 	@PIPENV_VENV_IN_PROJECT=1 pipenv sync --dev --keep-outdated
+	rm -f pyproject.toml
 	@touch .venv
 
 .PHONY: check-pipenv
@@ -91,6 +92,7 @@ check-tox:
 .PHONY: clean
 clean:
 	python3 setup.py clean --all
+	rm -f pyproject.toml
 
 .PHONY: distclean
 distclean: clean