tox fails with pippy is not allowed

[jaraco]

 csv2ofx master $ tox --version
4.5.2 from /Users/jaraco/.local/pipx/venvs/tox/lib/python3.11/site-packages/tox/__init__.py
 csv2ofx master $ tox
py: install_deps> helpers/pippy -r /Users/jaraco/code/reubano/csv2ofx/dev-requirements.txt -r /Users/jaraco/code/reubano/csv2ofx/requirements.txt
py: failed with /Users/jaraco/code/reubano/csv2ofx/helpers/pippy (resolves to /Users/jaraco/code/reubano/csv2ofx/helpers/pippy) is not allowed, use allowlist_externals to allow it
  py: FAIL code 1 (0.02 seconds)
  evaluation failed :( (0.05 seconds)

[jaraco]

(elided)

I realize now that's a separate issue so will report it separately.