bug#39757: python@3.7 + poetry: poetry is broken

[Francesco Frassinelli]

$ guix environment --ad-hoc python@3.7 poetry -- poetry --help
substitute:
/gnu/store/q19l04vd2za80mk1845pz7r8cz29qk43-bash-minimal-4.4.23/bin/bash:
warning: setlocale: LC_ALL: cannot change locale (en_US.utf8)
substitute:
/gnu/store/q19l04vd2za80mk1845pz7r8cz29qk43-bash-minimal-4.4.23/bin/bash:
warning: setlocale: LC_ALL: cannot change locale (en_US.utf8)
Traceback (most recent call last):
  File
"/gnu/store/c9vg9n69zic2zjzbvqsc12mglkdipws8-poetry-0.12.17/bin/.poetry-real",
line 11, in <module>
    load_entry_point('poetry==0.12.17', 'console_scripts', 'poetry')()
  File
"/gnu/store/608bvypsh90c58apvd2cgg3m9l2pwjqn-python-3.7.4/lib/python3.7/site-packages/pkg_resources/__init__.py",
line 489, in load_entry_point
    return get_distribution(dist).load_entry_point(group, name)
  File
"/gnu/store/608bvypsh90c58apvd2cgg3m9l2pwjqn-python-3.7.4/lib/python3.7/site-packages/pkg_resources/__init__.py",
line 2793, in load_entry_point
    return ep.load()
  File
"/gnu/store/608bvypsh90c58apvd2cgg3m9l2pwjqn-python-3.7.4/lib/python3.7/site-packages/pkg_resources/__init__.py",
line 2411, in load
    return self.resolve()
  File
"/gnu/store/608bvypsh90c58apvd2cgg3m9l2pwjqn-python-3.7.4/lib/python3.7/site-packages/pkg_resources/__init__.py",
line 2417, in resolve
    module = __import__(self.module_name, fromlist=['__name__'], level=0)
  File
"/gnu/store/sfjm1g50503x5j9qhfq9kfgqbdvw421g-profile/lib/python3.7/site-packages/poetry/console/__init__.py",
line 1, in <module>
    from .application import Application
  File
"/gnu/store/sfjm1g50503x5j9qhfq9kfgqbdvw421g-profile/lib/python3.7/site-packages/poetry/console/application.py",
line 7, in <module>
    from cleo.formatters import Formatter
ModuleNotFoundError: No module named 'cleo.formatters'
$ guix search poetry | recsel -P version
0.12.17
$ curl -sI HEAD https://github.com/python-poetry/poetry/releases/latest
| grep Location
Location: https://github.com/python-poetry/poetry/releases/tag/1.0.3

--
Frafra