How to fix ModuleNotFoundError: No module named 'virtualenv'

ModuleNotFoundError: No module named 'virtualenv'
Recommended: Install via pip into your active environment.
python -m pip install virtualenv

Verification

Command
python -c "import virtualenv; print(virtualenv.__version__)"
Expected output
Success! virtualenv version x.y.z (e.g., 2.4.0)