This is a followup of MDL-60611, were phpunit6 support was added to 3.4.

With that integrated, we should be able to verify that plugins using the cool moodle-pligin-ci are able to be tested agains 3.4 branches with all current supported PHP versions (70,71 and 72). No changes need to be verified in older branches, just 34 (master right now).

Ciao