The recommended version of get is 2.7.4 or later. Check the installed version of git in the Ubuntu VM:
git --version
Create an SSH key to user with gerrit. Use no passphrase.
ssh-keygen -t rsa
Install the git-review package.
sudo apt update
sudo apt install git-review
Get VirtualBox and VirtualBox Guest Additions
Make sure you have the VirtualBox Guest Additions ISO for your version of VirtualBox. I'm using VirtualBox 5.1.28. Save the Guest Additions ISO on your host computer along with the Ubuntu ISO. Get the Guest Additions ISO from here:
http://download.virtualbox.org/virtualbox
NOTE: Guest Additions versions prior to 5.1 will not work with Ubuntu 16.04.3. If you have an earlier version of VirtualBox, you should upgrade to the latest 5.1 version.