Mojo: Continuous Delivery for Juju

Merge proposals dependent on lp://staging/~pjdc/mojo/juju-2-no-fail-when-retrying-errors

  1. juju-2-no-fail-when-retrying-errors
  2. Dependent merge proposals

lp://staging/~pjdc/mojo/juju-2-no-fail-when-retrying-errors has no merge proposals.