Tox tests fail if py37 is not present

[adriangonz]

tox is configured to run the tests on a py37 environment. However, if Python 3.7 is not present the tests fail.

seldon-core/python/setup.cfg

Line 6 in 1ae7957

py37

It seems that tox doesn't do anything besides checking if there is a python3.7 interpreter present. We should either change tox's config to run the tests on whatever environment is present or add some way for tox to fetch the relevant versions if they are not present.

[axsaucedo]

@adriangonz is this something we want for 1.1 or push for later?

[adriangonz]

@adriangonz I think it would be good to have a look for 1.1. I can have a look into it and while I'm there I can also add tests for Python 3.8.