See for example this build: https://travis-ci.org/piwik/piwik/jobs/269332115
Guess it has something to do with the return code, as we return the failure count, which seems to be 255 in that build.
There was also this build: https://travis-ci.org/piwik/piwik/jobs/277594128
it had 253 successful tests (not 255) yet the builds also appears as failed?
@sgiehl @mneudert do you maybe have some idea how to fix this issue? it'd be great to get this fixed and see our green UI builds