[FIX] .gitlab-ci.yml: turn off nonblocking
This is a possible fix to the flaky error affecting our builds, requested in the issue#5961
More info: https://github.com/travis-ci/travis-ci/issues/4704#issuecomment-348435959
This is a possible fix to the flaky error affecting our builds, requested in the issue#5961
More info: https://github.com/travis-ci/travis-ci/issues/4704#issuecomment-348435959