Change python on travis to 3.6 to avoid error (#171)
Change python on travis to 3.6 to avoid error (#171)

I've tried various fixes like:
```
python:
  - 3.6
```
in the .travis.yml file, but none worked (see travis-ci/travis-ci/issues/8363). Keeping `pyenv global system` and simply changing the version to 3.6 worked though.
patrikhuber/eos,patrikhuber/eos,patrikhuber/eos