error from pypa build

[Robin Becker]

I'm building a pure python wheel in a python3.9 virtualenv.

If I use python setup.py bdist_wheel I do get a wheel named

rlextra-3.6.0-py3-none-any.whl

I'm trying out building a modern python 3 only wheel so I followed instructions here

https://packaging.python.org/tutorials/packaging-projects/#creating-the-package-files

and see the error below which is not very informative. Any ideas of what's wrong? I still get the error even after 
upgrading pip so I don't think that is the problem.

 > (.py39) user at pc:~/devel/reportlab/REPOS/rlextra
 > $ pip install build
 > Collecting build
 >   Downloading build-0.5.1-py2.py3-none-any.whl (15 kB)
 > Collecting pep517>=0.9.1
 > ..........
 > Installing collected packages: tomli, pyparsing, toml, pep517, packaging, build
 > Successfully installed build-0.5.1 packaging-21.0 pep517-0.11.0 pyparsing-2.4.7 toml-0.10.2 tomli-1.2.0
 > WARNING: You are using pip version 21.1.3; however, version 21.2.2 is available.
 > You should consider upgrading via the '/home/user/devel/reportlab/.py39/bin/python39 -m pip install --upgrade pip' 
command.
 > (.py39) user at pc:~/devel/reportlab/REPOS/rlextra
 > $ ls
 > build  dist  docs  examples  LICENSE.txt  README.txt  setup.cfg  setup.py  src  tests  tmp
 > (.py39) user at pc:~/devel/reportlab/REPOS/rlextra
 > $ python -m build --wheel
 > Traceback (most recent call last):
 >   File "/home/user/devel/reportlab/.py39/lib/python3.9/site-packages/build/__main__.py", line 302, in main
 >     build_call(args.srcdir, outdir, distributions, config_settings, not args.no_isolation, args.skip_dependency_check)
 >   File "/home/user/devel/reportlab/.py39/lib/python3.9/site-packages/build/__main__.py", line 145, in build_package
 >     _build(isolation, builder, outdir, distribution, config_settings, skip_dependency_check)
 >   File "/home/user/devel/reportlab/.py39/lib/python3.9/site-packages/build/__main__.py", line 101, in _build
 >     return _build_in_isolated_env(builder, outdir, distribution, config_settings)
 >   File "/home/user/devel/reportlab/.py39/lib/python3.9/site-packages/build/__main__.py", line 77, in 
_build_in_isolated_env
 >     with IsolatedEnvBuilder() as env:
 >   File "/home/user/devel/reportlab/.py39/lib/python3.9/site-packages/build/env.py", line 92, in __enter__
 >     executable, scripts_dir = _create_isolated_env_venv(self._path)
 >   File "/home/user/devel/reportlab/.py39/lib/python3.9/site-packages/build/env.py", line 221, in 
_create_isolated_env_venv
 >     pip_distribution = next(iter(metadata.distributions(name='pip', path=[purelib])))
 > StopIteration
 >
 > ERROR
 > (.py39) user at pc:~/devel/reportlab/REPOS/rlextra

thanks for any assistance
--
Robin Becker