If you encounter the following error when doing apt-get update (for instance, before installing a package):

The method driver /usr/lib/apt/methods/https could not be found

Then it means that you lack the apt-transport-https package. You can install it by doing:

sudo apt-get install apt-transport-https

If you have already added an HTTPS enabled repository in your /etc/apt/sources.list.d/ folder, then you'll need to remove it first.