I nearly installed everything, but when I try to run ./install.sh I'm stuck at the following error: "Package 'python-virtualenv' has no installation candidate" I installed the python3-virtualenv, but ...

Put pyv in your PATH. Put the requirements for a script foo.py in a file foo.pyv. Run your script using pyv instead of python. Python has a large collection of useful software libraries, via pypi. For ...