molecule: master: pip install -e . fails with TypeError: expected str, bytes or os.PathLike object, not NoneType

The problem seems to be related to recent pep517/setuptools/packaging changes but is really worrig because it totally breaks packaging.

$ pip install -e .                                                                                                                                                                                                                            [15:59:21]
Obtaining file:///Users/ssbarnea/os/molecule
  Installing build dependencies ... done
  Getting requirements to build wheel ... done
    Preparing wheel metadata ... error
    Complete output from command /Users/ssbarnea/rdo/tripleo-ci/.tox/molecule/bin/python3.6 /Users/ssbarnea/rdo/tripleo-ci/.tox/molecule/lib/python3.6/site-packages/pip/_vendor/pep517/_in_process.py prepare_metadata_for_build_wheel /var/folders/3q/pc1jcyjj3qqbj6_x7n4kbtqw0000gn/T/tmpjmy837ev:
    running dist_info
    creating /Users/ssbarnea/os/molecule/pip-wheel-metadata/molecule.egg-info
    writing /Users/ssbarnea/os/molecule/pip-wheel-metadata/molecule.egg-info/PKG-INFO
    writing dependency_links to /Users/ssbarnea/os/molecule/pip-wheel-metadata/molecule.egg-info/dependency_links.txt
    writing entry points to /Users/ssbarnea/os/molecule/pip-wheel-metadata/molecule.egg-info/entry_points.txt
    writing requirements to /Users/ssbarnea/os/molecule/pip-wheel-metadata/molecule.egg-info/requires.txt
    writing top-level names to /Users/ssbarnea/os/molecule/pip-wheel-metadata/molecule.egg-info/top_level.txt
    writing manifest file '/Users/ssbarnea/os/molecule/pip-wheel-metadata/molecule.egg-info/SOURCES.txt'
    reading manifest template 'MANIFEST.in'
    writing manifest file '/Users/ssbarnea/os/molecule/pip-wheel-metadata/molecule.egg-info/SOURCES.txt'
    creating '/Users/ssbarnea/os/molecule/pip-wheel-metadata/molecule.dist-info'
    Traceback (most recent call last):
      File "/Users/ssbarnea/rdo/tripleo-ci/.tox/molecule/lib/python3.6/site-packages/pip/_vendor/pep517/_in_process.py", line 207, in <module>
        main()
      File "/Users/ssbarnea/rdo/tripleo-ci/.tox/molecule/lib/python3.6/site-packages/pip/_vendor/pep517/_in_process.py", line 197, in main
        json_out['return_val'] = hook(**hook_input['kwargs'])
      File "/Users/ssbarnea/rdo/tripleo-ci/.tox/molecule/lib/python3.6/site-packages/pip/_vendor/pep517/_in_process.py", line 69, in prepare_metadata_for_build_wheel
        return hook(metadata_directory, config_settings)
      File "/Users/ssbarnea/.pyenv/versions/3.6.7/lib/python3.6/site-packages/setuptools/build_meta.py", line 113, in prepare_metadata_for_build_wheel
        _run_setup()
      File "/Users/ssbarnea/.pyenv/versions/3.6.7/lib/python3.6/site-packages/setuptools/build_meta.py", line 72, in _run_setup
        exec(compile(code, __file__, 'exec'), locals())
      File "setup.py", line 351, in <module>
        __name__ == '__main__' and setuptools.setup(**setup_params)
      File "/Users/ssbarnea/.pyenv/versions/3.6.7/lib/python3.6/site-packages/setuptools/__init__.py", line 129, in setup
        return distutils.core.setup(**attrs)
      File "/Users/ssbarnea/.pyenv/versions/3.6.7/lib/python3.6/distutils/core.py", line 148, in setup
        dist.run_commands()
      File "/Users/ssbarnea/.pyenv/versions/3.6.7/lib/python3.6/distutils/dist.py", line 955, in run_commands
        self.run_command(cmd)
      File "/Users/ssbarnea/.pyenv/versions/3.6.7/lib/python3.6/distutils/dist.py", line 974, in run_command
        cmd_obj.run()
      File "setup.py", line 323, in run
        return setuptools.command.dist_info.dist_info.run(self)
      File "/Users/ssbarnea/.pyenv/versions/3.6.7/lib/python3.6/site-packages/setuptools/command/dist_info.py", line 36, in run
        bdist_wheel.egg2dist(egg_info.egg_info, dist_info_dir)
      File "/Users/ssbarnea/.pyenv/versions/3.6.7/lib/python3.6/site-packages/wheel/bdist_wheel.py", line 443, in egg2dist
        shutil.copy(license, os.path.join(self.distinfo_dir, license_filename))
      File "/Users/ssbarnea/rdo/tripleo-ci/.tox/molecule/lib/python3.6/posixpath.py", line 80, in join
        a = os.fspath(a)
    TypeError: expected str, bytes or os.PathLike object, not NoneType

    ----------------------------------------
Command "/Users/ssbarnea/rdo/tripleo-ci/.tox/molecule/bin/python3.6 /Users/ssbarnea/rdo/tripleo-ci/.tox/molecule/lib/python3.6/site-packages/pip/_vendor/pep517/_in_process.py prepare_metadata_for_build_wheel /var/folders/3q/pc1jcyjj3qqbj6_x7n4kbtqw0000gn/T/tmpjmy837ev" failed with error code 1 in /Users/ssbarnea/os/molecule