Hi,
this is a typical Python installation issue. You need to understand Python modules and how they get loaded from the interpreter. Python virtual environments help you to separate installations to be able to install different versions of one module. Please read https://realpython.com/python-virtual-environments-a-primer/ for an introduction to virtual environments.
To fix your issue please create a fresh new virtual Python environment, activate that environment (source /path/to/env/bin/activate), update pip in the environment (pip install -U pip) and afterwards install gvm-tools without --user switch (pip install gvm-tools). You don’t need (and even can’t use) the --user option within virtual environments. It even doesn’t make sense if you understand them.