The problem was that a tagged revision is not deployed, so after a
release we did an empty commit to trigger deployment. Now it is worked
around by adding extra deployment rules that deploys tagged revisions.
The workaround was suggested by Hiro Asari in [1].

[1]: https://github.com/travis-ci/travis-ci/issues/7780#issuecomment-302389370

Fixes #3745.