Description of problem:
In recent state of Katello there is thrown an error (no details in: {pulp.log,catalina.out,production.log}) during promoting an errata.
---
Changeset [ cs_Dev2 ] promotion failed: undefined method `merge' for #<JSON::Ext::Generator::State:0x7fef87937550>

Version-Release number of selected component (if applicable):
katello-cli-0.1.54-3.el6.noarch
katello-0.1.235-2.el6.noarch
pulp-0.0.265-1.el6.noarch
candlepin-0.5.18-1.el6.noarch


How reproducible:
always

Steps to Reproduce:
Do following from Katello cli shell:
---
> org create --name "Zoo Corporation"
> client remember --option org --value "Zoo Corporation"
> provider create --name Zoo
> product create --name Zoo --provider Zoo
> repo create --product Zoo --url http://inecas.fedorapeople.org/fakerepos/zoo/ --name zoo-repo
> environment create --name Dev --prior Library
> changeset create --name cs_Dev1 --environment Dev
> changeset update --add_product Zoo --name cs_Dev1 --environment Dev
> changeset promote --name cs_Dev1 --environment Dev
> repo synchronize --name zoo-repo --product Zoo
> errata list --repo zoo-repo --product Zoo 
> changeset update --from_product Zoo --add_erratum RHEA-2012:0002 --name cs_Dev2 --environment Dev
> changeset promote --name cs_Dev2 --environment Dev
---

but despite of the error the promotion is done.
---
> errata info --repo zoo-repo --product Zoo --environment Dev --id RHEA-2012:0002


Actual results:
Exception thrown (however promotion is done)

Expected results:
no exception, clean output ;)

Additional info: