First install ntplib in your computer.

$ sudo apt-get install python-ntplib

ntplib works on Python 2. You may install python3-ntplib that works for Python 3 from https://launchpad.net/ubuntu/yakkety/amd64/python3-ntplib/0.3.3-1, or by following the succeeding commands:

$ wget http://launchpadlibrarian.net/260811286/python3-ntplib_0.3.3-1_all.deb
$ sudo dpkg -i python3-ntplib_0.3.3-1_all.deb