症状

The following error appears in the logs:

More than one old Create Job post-function was defined for workflow transition 'rhubarb'
- they will be merged into ONE post-function under the new namespace.

原因

This means that, pre-upgrade, you had more than one Create Job post-function configured for a particular workflow transition. This is typically redundant, so the upgrade process automatically merges them into one (which is placed in the position of the first Create Job post-function encountered).

ソリューション

If you really wanted two instances of the Create Job post-function (ie. you have custom code that relies on it - two instances will not generally create two jobs) you can still manually add it after the initial upgrade. The upgrade process will not attempt to merge instances of the new version of the post-function.