Documentation builds failing in keystone-specs

When running tox for the first time (i.e., creating virtualenv), the following errors occur. This also happens on Zuul and thus we can't see the built document on Gerrit. This error will be gone by removing setup.py and setup.cfg like Nova did [1].

[1] https://github.com/openstack/nova-specs/commit/604cc59adaa0f2d42746fdbf18e9af5eea94efc4

$ tox -e pep8
pep8 create: /home/stack/keystone-specs/.tox/pep8
pep8 installdeps: -r/home/stack/keystone-specs/requirements.txt
pep8 develop-inst: /home/stack/keystone-specs
ERROR: invocation failed (exit code 1), logfile: /home/stack/keystone-specs/.tox/pep8/log/pep8-2.log
======================================================================================================================================================== log start =========================================================================================================================================================
Obtaining file:///home/stack/keystone-specs
  Preparing metadata (setup.py): started
  Preparing metadata (setup.py): finished with status 'error'
  error: subprocess-exited-with-error

  × python setup.py egg_info did not run successfully.
  │ exit code: 1
  ╰─> [30 lines of output]
      /home/stack/keystone-specs/.tox/pep8/lib/python3.10/site-packages/setuptools/dist.py:757: UserWarning: Usage of dash-separated 'description-file' will not be supported in future versions. Please use the underscore name 'description_file' instead
        warnings.warn(
      /home/stack/keystone-specs/.tox/pep8/lib/python3.10/site-packages/setuptools/dist.py:757: UserWarning: Usage of dash-separated 'author-email' will not be supported in future versions. Please use the underscore name 'author_email' instead
        warnings.warn(
      /home/stack/keystone-specs/.tox/pep8/lib/python3.10/site-packages/setuptools/dist.py:757: UserWarning: Usage of dash-separated 'home-page' will not be supported in future versions. Please use the underscore name 'home_page' instead
        warnings.warn(
      /home/stack/keystone-specs/.tox/pep8/lib/python3.10/site-packages/setuptools/command/easy_install.py:144: EasyInstallDeprecationWarning: easy_install command is deprecated. Use build and pip and other standards-based tools.
        warnings.warn(
      /home/stack/keystone-specs/.tox/pep8/lib/python3.10/site-packages/setuptools/command/install.py:34: SetuptoolsDeprecationWarning: setup.py install is deprecated. Use build and pip and other standards-based tools.
        warnings.warn(
      /home/stack/keystone-specs/.tox/pep8/lib/python3.10/site-packages/setuptools/dist.py:757: UserWarning: Usage of dash-separated 'description-file' will not be supported in future versions. Please use the underscore name 'description_file' instead
        warnings.warn(
      /home/stack/keystone-specs/.tox/pep8/lib/python3.10/site-packages/setuptools/dist.py:757: UserWarning: Usage of dash-separated 'author-email' will not be supported in future versions. Please use the underscore name 'author_email' instead
        warnings.warn(
      /home/stack/keystone-specs/.tox/pep8/lib/python3.10/site-packages/setuptools/dist.py:757: UserWarning: Usage of dash-separated 'home-page' will not be supported in future versions. Please use the underscore name 'home_page' instead
        warnings.warn(
      error: Multiple top-level packages discovered in a flat-layout: ['specs', 'attic', 'superseded'].

      To avoid accidental inclusion of unwanted files or directories,
      setuptools will not proceed with this build.

      If you are trying to create a single distribution with multiple packages
      on purpose, you should not rely on automatic discovery.
      Instead, consider the following options:

      1. set up custom discovery (`find` directive with `include` or `exclude`)
      2. use a `src-layout`
      3. explicitly set `py_modules` or `packages` with a list of names

      To find more information, look for "package discovery" on setuptools docs.
      [end of output]

  note: This error originates from a subprocess, and is likely not a problem with pip.
error: metadata-generation-failed

× Encountered error while generating package metadata.
╰─> See above for output.

note: This is an issue with the package mentioned above, not pip.
hint: See above for details.
WARNING: You are using pip version 22.0.4; however, version 22.1.1 is available.
You should consider upgrading via the '/home/stack/keystone-specs/.tox/pep8/bin/python -m pip install --upgrade pip' command.

========================================================================================================================================================= log end ==========================================================================================================================================================
_________________________________________________________________________________________________________________________________________________________ summary __________________________________________________________________________________________________________________________________________________________
ERROR: pep8: InvocationError for command /home/stack/keystone-specs/.tox/pep8/bin/python -m pip install --exists-action w -e . (exited with code 1)