erp5_forge: Display failure to push as error

See merge request !1812
4 jobs for master in 0 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  External
failed ERP5.CodingStyleTest-Master

00:47:22

failed ERP5.UnitTest-Master

01:43:50

failed ERP5.UnitTest-Zope2

01:55:39

passed Wendelin.UnitTest-Master

00:44:02