apt-transport-https software package provides https download transport for APT, you can install in your Ubuntu 16.04 LTS (Xenial Xerus) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install apt-transport-https
apt-transport-https is installed in your system.
Make ensure the apt-transport-https package were installed using the commands given below,
$ sudo dpkg-query -l | grep apt-transport-https *
You will get with apt-transport-https package name, version, architecture and description in a table
| Distro | Ubuntu 16 04 lts xenial xerus |
| Section | Administration Utilities |
| Package | apt-transport-https |
| Version | 1.2.10ubuntu1 |
| Description | https download transport for APT |
| Sub Section | admin |