Running bash <(curl -s https://tinker.bunq.com/python/setup.sh) returned
Could not find "pipenv", try installing it by running "pip install pipenv".
even thoughpip list does show pipenv and pip install pipenv says it is already installed.
The problem is that which pipenv (which setup.py runs to verify it being present) indeed returned nothing. I was able to fix this by installing it again through brew install pipenv which does install itself in the user's path:
$ which pipenv
/usr/local/bin/pipenv