Upgrading from stable to devel charm breaks clients

After upgrading the rabbitmq-server charm from the stable version to the next (devel) version clients could no longer connect.
The rabbit logs showed:
...
=ERROR REPORT==== 3-Aug-2015::12:05:51 ===
closing AMQP connection <0.13457.0> (10.5.39.129:40991 -> 10.5.39.128:5672):
{handshake_error,starting,0,
                 {amqp_error,access_refused,
                             "AMQPLAIN login refused: user 'nova' - invalid credentials",
                             'connection.start_ok'}}

=ERROR REPORT==== 3-Aug-2015::12:05:52 ===
closing AMQP connection <0.13461.0> (10.5.39.121:39746 -> 10.5.39.128:5672):
{handshake_error,starting,0,
                 {amqp_error,access_refused,
                             "AMQPLAIN login refused: user 'neutron' - invalid credentials",
                             'connection.start_ok'}}

=ERROR REPORT==== 3-Aug-2015::12:05:52 ===
closing AMQP connection <0.13464.0> (10.5.39.127:43251 -> 10.5.39.128:5672):
{handshake_error,starting,0,
                 {amqp_error,access_refused,
                             "AMQPLAIN login refused: user 'nova' - invalid credentials",
                             'connection.start_ok'}}
...

the password being used by the client was consistent with the password being sent by rabbit:

juju run --unit neutron-gateway/0 "relation-get -r amqp:45 - rabbitmq-server/0"
hostname: 10.5.39.128
password: YxMpxJtTc33g637prBdptgSpk7hthSjSjmYqm6pW32SHPm9yqWscfWwZW9XqwgWL
private-address: 10.5.39.128

 juju run --unit neutron-gateway/0 "grep rabbit /etc/neutron/neutron.conf"
rabbit_userid = neutron
rabbit_virtual_host = openstack
rabbit_password = YxMpxJtTc33g637prBdptgSpk7hthSjSjmYqm6pW32SHPm9yqWscfWwZW9XqwgWL
rabbit_host = 10.5.39.128
list_notifier_drivers = neutron.openstack.common.notifier.rabbit_notifier

changing the password via rabbitmqctl to the one being used by the client fixed the issue