"source" config option does not support "cloud:" source

Hello,

Settings the "source:" value to "cloud:xenial-ocata" does not work. Getting the following error:

---
INFO install Preparing to unpack .../ubuntu-cloud-keyring_2012.08.14_all.deb ...
INFO install Unpacking ubuntu-cloud-keyring (2012.08.14) ...
INFO install Setting up ubuntu-cloud-keyring (2012.08.14) ...
INFO install Importing ubuntu-cloud.archive.canonical.com keyring
INFO install OK
INFO install Processing ubuntu-cloud.archive.canonical.com removal keyring
INFO install gpg: /etc/apt/trustdb.gpg: trustdb created
INFO install OK
INFO install Traceback (most recent call last):
INFO install File "/var/lib/juju/agents/unit-glance-simplestreams-sync-0/charm/hooks/install.real", line 290, in <module>
INFO install hooks.execute(sys.argv)
INFO install File "/var/lib/juju/agents/unit-glance-simplestreams-sync-0/charm/hooks/charmhelpers/core/hookenv.py", line 704, in execute
INFO install self._hooks[hook_name]()
INFO install File "/var/lib/juju/agents/unit-glance-simplestreams-sync-0/charm/hooks/install.real", line 206, in install
INFO install add_source(hookenv.config('source'), hookenv.config('key'))
INFO install File "/var/lib/juju/agents/unit-glance-simplestreams-sync-0/charm/hooks/charmhelpers/fetch/__init__.py", line 289, in add_source
INFO install pocket)
INFO install charmhelpers.fetch.SourceConfigError: Unsupported cloud: source option xenial-ocata
ERROR juju.worker.uniter.operation runhook.go:107 hook "install" failed: exit status 1
DEBUG juju.worker.uniter.operation executor.go:84 lock released
INFO juju.worker.uniter resolver.go:100 awaiting error resolution for "install" hook
DEBUG juju.worker.uniter agent.go:17 [AGENT-STATUS] error: hook failed: "install"
DEBUG juju.worker.uniter.remotestate watcher.go:434 retry hook timer triggered
---

Resetting this value resolves this error.