ModuleNotFoundError: No module named 'cleo'

• I am on the latest Poetry version.
• I have searched the issues of this repo and believe that this is not a duplicate.
• If an exception occurs when executing a command, I executed it again in debug mode (-vvv option).

• OS: Mac OS X / 10.14.6 / 18G5033
• Poetry version: 1.1.0
• Python version: 3.8

Issue

After updating poetry to 1.1.0 with poetry self update, it stopped working. I cannot run even poetry --version now.

$ poetry self update
Updating to 1.1.0
 - Downloading poetry-1.1.0-darwin.tar.gz 100%

Poetry (1.1.0) is installed now. Great!

$ poetry
Traceback (most recent call last):
  File "/Users/username/.poetry/bin/poetry", line 12, in <module>
    from poetry.console import main
  File "/Users/username/.poetry/lib/poetry/console/__init__.py", line 1, in <module>
    from .application import Application
  File "/Users/username/.poetry/lib/poetry/console/application.py", line 3, in <module>
    from cleo import Application as BaseApplication
ModuleNotFoundError: No module named 'cleo'

$ poetry --version
Traceback (most recent call last):
  File "/Users/username/.poetry/bin/poetry", line 12, in <module>
    from poetry.console import main
  File "/Users/username/.poetry/lib/poetry/console/__init__.py", line 1, in <module>
    from .application import Application
  File "/Users/username/.poetry/lib/poetry/console/application.py", line 3, in <module>
    from cleo import Application as BaseApplication
ModuleNotFoundError: No module named 'cleo'

I searched for an issue but couldn’t find one. #2991 was for a different problem.