Chandan Singh authored Aug 21, 2018 and Tristan Van Berkom committed Aug 21, 2018

These new images come with pinned versions of `pytest` and `pylint`:

- `pylint`: `== 2.1.1`
- `pytest`: `>= 3.7`

Chandan Singh authored Aug 21, 2018 and Tristan Van Berkom committed Aug 21, 2018

These packages should only be updated as a deliberate change and the
code should be tested with the new versions to ensure that the test
still pass.

Any future updates should also happen in sync with the
buildstream-docker-images repository so that the testsuite base images
also enforce the same restrictions for the development requirements.

Replaces !684.

Restrict pylint/pytest versions and bump CI tags

See merge request !689