Updating CI so focal distro images is used with python 2.7, 3.6, and 3.7

[jswongF5]

Reviewers

@alankrit8

Issue

Travis CI was failing during deployment to PyPi

Fixes:
Updated CI build image to use bionic instead of the xenial default.

Describe the problem/feature to which this change applies

The pipeline suddenly failed to deploy to PyPi with the following error message.

Installing deploy dependencies
Successfully installed dpl-pypi-1.10.16
1 gem installed
2022-04-05 20:51:56 URL:https://bootstrap.pypa.io/get-pip.py [2658865/2658865] -> "-" [1]
ERROR: This script does not work on Python 3.6 The minimum supported Python version is 3.7. Please use https://bootstrap.pypa.io/pip/3.6/get-pip.py instead.
Couldn't install pip, setuptools, twine or wheel.

failed to deploy

Describe the change(s) made and why

Updating the Travis CI image from using xenial to bionic