bug 1399639: Upgrade raven (for sentry) to 6.2.1
bug 1399639: Upgrade raven (for sentry) to 6.2.1

* raven 5.10.2 → 6.2.1: Breadcrumb support, update Django support, many
  bug fixes and small features.

mozilla/kuma,escattone/kuma,mozilla/kuma,mozilla/kuma,a2sheppy/kuma,SphinxKnight/kuma,Elchi3/kuma,Elchi3/kuma,SphinxKnight/kuma,jwhitlock/kuma,Elchi3/kuma,mozilla/kuma,Elchi3/kuma,jwhitlock/kuma,escattone/kuma,a2sheppy/kuma,a2sheppy/kuma,SphinxKnight/kuma,SphinxKnight/kuma,escattone/kuma,SphinxKnight/kuma,a2sheppy/kuma,Elchi3/kuma,jwhitlock/kuma,jwhitlock/kuma,SphinxKnight/kuma,jwhitlock/kuma,a2sheppy/kuma,mozilla/kuma