Tox+Python: WinError 5 Access denied (despite running as admin)

I'm getting crazy from this problem.

I'm using Tox for testing my Python package and suddenly I started getting this error:

When I try to recreate my tox environment (tox --recreate), it keeps failing with the "WinError 5: Access is denied"

Could not install packages due to an EnvironmentError: [WinError 5] Access is denied: 'C:\\Users\\NRADOJ~1\\AppData\\Local\\Temp\\pip-unpack-bumke6sa\\scipy-1.1.0-cp36-none-win_amd64.whl' Consider using the--useroption or check the permissions.

All suggestions I found online were "Run the command prompt as admin", but that doesn't work for me...

It seems that the error is thrown when pip attempts to clean up the temp directory from the downloaded .whl file for SciPy.

Any ideas?