Support Python 3.8 on Xenial / Ubuntu 16

[samuelgundry]

Users would like to use more recent versions of Python for bundling than the default installed with Xenial, Python 3.5.

Is it possible to use python3.8 -m pip ... ?

[murphm8]

We could add a --python3-version which would accept a canonical Python verison number eg. 3.5, 3.6, 3.7, 3.8.

During python installation the user would have to set up a PPA to install the correct version of python: https://launchpad.net/~deadsnakes/+archive/ubuntu/ppa

Then we would need to install based on the argument and use the correct python version based on the argument. pip is included by default in 3.4+ so we could continue to do installation of dependencies like we do now with python3.X -m pip install ....

"pip is the preferred installer program. Starting with Python 3.4, it is included by default with the Python binary installers."

• https://docs.python.org/3/installing/index.html