by 
The default pip version for Ubuntu 16.04 is 2.7 which is quite outdated. For instance, it is impossible to get mpsyt to work with pip 2.7. Any attempt to install pip3 using sudo apt install python3-pip will be resulted in getting this message:
python3-pip is already the newest version (8.1.1-2ubuntu0.4).
Fortunately, there is an easy way to workaround this issue:
$ sudo apt-get install python3-setuptools
$ sudo easy_install3 pip
Enjoy pip 3 in Ubuntu 16.04!
