stack/erp5: handle coverage reporting from erp5.git

This now supports producing html reports directly
4 jobs for feat/coverage in 0 seconds
latest
Status Job ID Name Coverage
  External
failed ERP5.UnitTest-Feat-Coverage-Jerome

03:22:14

failed ERP5.UnitTest-Feat-Coverage-Jerome

04:00:57

failed ERP5.UnitTest-Feat-Coverage-Jerome

03:05:17

canceled ERP5.UnitTest-Feat-Coverage-Jerome

07:53:13