The `.travis.yml` file currently states that the test with GHC 8.6 is allowed to fail. But should it be?
Since 8.6 was initially included in `.travis.yml`, the compiler has matured and even 8.8 has been released now. Compilation seems to consistently succeed for that version: https://travis-ci.org/ivanperez-keera/Yampa/builds/594563304
I believe compilation should no longer be allowed to fail with 8.6, and perhaps it should be with 8.8 (#141), as per https://github.com/ivanperez-keera/Yampa/pull/143#issuecomment-539100674.