We use our own CI environment. We have Jenkins servers on our machines.
The problem with travis is that we would probably violate fair use policy. Our full test suite generates some gigabytes of data, using all 8 cores of CPU for like 10 minutes. it's not an option to run it on travis.
We use TOX, pytest and Jenkins. So switching to travis doesn't make sense at all there. It's strongly integrated with our tools etc. Sorry for that but we can't support 2 different test setups right now.