sudo apt install python3-venv
sudo apt install python3.4-venv
sudo apt-get install python3-venv
sudo apt-get install python3.4-venv
sudo apt-get install -y python3-venv
sudo apt-get install -y python3.4-venv

Package python3-venv is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or is only available from another source.
E: Package 'python3-venv' has no installation candidate