pipenv install error ImportError: cannot import name 'ensure_file_on_disk'

I'm trying to create a python virtual environment with pipenv 2018.11.26 on Windows [Version 10.0.14393] and Python 3.5.2 (Anaconda 4.1.1 (64-bit)). These are all mandatory settings that I can't alter.

I get the following cryptic error:

C:\project_path\pipenv install

Creating a virtualenv for this project…
Pipfile: C:\project_path\Pipfile
Using C:/Anaconda3/pythonw.exe (3.5.2) to create virtualenv…
[  ==] Creating virtual environment...ImportError: cannot import name 'ensure_file_on_disk'

Failed creating virtual environment
[pipenv.exceptions.VirtualenvCreationException]:   File "c:\anaconda3\lib\site-        packages\pipenv\cli\command.py", line 254, in install
[pipenv.exceptions.VirtualenvCreationException]:           editable_packages=state.installstate.editables,
[pipenv.exceptions.VirtualenvCreationException]:   File "c:\anaconda3\lib\site-    packages\pipenv\core.py", line 1741, in do_install
[pipenv.exceptions.VirtualenvCreationException]:       pypi_mirror=pypi_mirror,
[pipenv.exceptions.VirtualenvCreationException]:   File "c:\anaconda3\lib\site-    packages\pipenv\core.py", line 574, in ensure_project
[pipenv.exceptions.VirtualenvCreationException]:       pypi_mirror=pypi_mirror,
[pipenv.exceptions.VirtualenvCreationException]:   File "c:\anaconda3\lib\site-    packages\pipenv\core.py", line 506, in ensure_virtualenv
[pipenv.exceptions.VirtualenvCreationException]:       python=python, site_packages=site_packages,     pypi_mirror=pypi_mirror
[pipenv.exceptions.VirtualenvCreationException]:   File "c:\anaconda3\lib\site-    packages\pipenv\core.py", line 935, in do_create_virtualenv
[pipenv.exceptions.VirtualenvCreationException]:       extra=[crayons.blue("{0}".format(c.err)),]
[pipenv.exceptions.VirtualenvCreationException]:
Failed to create virtual environment.

The main cause sees to be an import error, but I can't find anything called ensure_file_on_disk.

I have tried to uninstall and re-install pipenv to no avail.

Also, since I'm running behind a proxy, I have created the system environment variables no_proxy, http_proxy and https_proxy but it hasn't worked either.

By the way if I try to run pipenv shell it gives me the exact same error, so it does not seem to be a connection problem after all.

Have you guys ever come across this issue?

Thanks