rabbitmq error and traceback when re-installing maas

Seeing problems re-installing maas during testing of cloud-installer:

1. install maas
2. uninstall maas (as part of cloud-uninstall script here: https://github.com/Ubuntu-Solutions-Engineering/cloud-installer/blob/master/tools/cloud-uninstall )
maas-relevant parts of that script:
    juju destroy-environment --yes --force maas
    rm -r ~/.maascli.db

    apt_purge '.*maas.*' 'bind9'
    sudo -u postgres psql -c 'drop database maasdb;'

3. re-install maas as part of the dependencies for the cloud installer

=> apt hangs - the following excerpt shows errors printed to the screen before it hangs.

Setting up rabbitmq-server (3.2.4-1) ...
 * Starting message broker rabbitmq-server [ OK ]
Setting up maas-region-controller (1.5+bzr2252-0ubuntu1) ...
 * Stopping web server apache2 *
 * Restarting PostgreSQL 9.3 database server [ OK ]
Considering dependency proxy for proxy_http:
Module proxy already enabled
Module proxy_http already enabled
Module expires already enabled
Module wsgi already enabled
 * Restarting message broker rabbitmq-server [ OK ]
Error: {'EXIT',
           {terminated,
               [{io,nl,[<0.30.0>],[]},
                {lists,foreach,2,[{file,"lists.erl"},{line,1323}]},
                {rabbit_control_main,display_info_list,2,
                    [{file,"src/rabbit_control_main.erl"},{line,651}]},
                {rabbit_control_main,start,0,
                    [{file,"src/rabbit_control_main.erl"},{line,156}]},
                {init,start_it,1,[]},
                {init,start_em,1,[]}]}}
Changing password for user "maas_longpoll" ...
...done.
Changing password for user "maas_workers" ...
...done.
Syncing...
Traceback (most recent call last):
  File "/usr/bin/django-admin", line 5, in <module>
    management.execute_from_command_line()
  File "/usr/lib/python2.7/dist-packages/django/core/management/__init__.py", line 399, in execute_from_command_line
    utility.execute()
  File "/usr/lib/python2.7/dist-packages/django/core/management/__init__.py", line 392, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/usr/lib/python2.7/dist-packages/django/core/management/base.py", line 242, in run_from_argv
    self.execute(*args, **options.__dict__)
  File "/usr/lib/python2.7/dist-packages/django/core/management/base.py", line 285, in execute
    output = self.handle(*args, **options)
  File "/usr/lib/python2.7/dist-packages/django/core/management/base.py", line 415, in handle
    return self.handle_noargs(**options)
  File "/usr/lib/python2.7/dist-packages/south/management/commands/syncdb.py", line 90, in handle_noargs
    syncdb.Command().execute(**options)
  File "/usr/lib/python2.7/dist-packages/django/core/management/base.py", line 285, in execute
    output = self.handle(*args, **options)
  File "/usr/lib/python2.7/dist-packages/django/core/management/base.py", line 415, in handle
    return self.handle_noargs(**options)
  File "/usr/lib/python2.7/dist-packages/django/core/management/commands/syncdb.py", line 57, in handle_noargs
    cursor = connection.cursor()
  File "/usr/lib/python2.7/dist-packages/django/db/backends/__init__.py", line 159, in cursor
    cursor = util.CursorWrapper(self._cursor(), self)
  File "/usr/lib/python2.7/dist-packages/django/db/backends/__init__.py", line 129, in _cursor
    self.ensure_connection()
  File "/usr/lib/python2.7/dist-packages/django/db/backends/__init__.py", line 124, in ensure_connection
    self.connect()
  File "/usr/lib/python2.7/dist-packages/django/db/utils.py", line 99, in __exit__
    six.reraise(dj_exc_type, dj_exc_value, traceback)
  File "/usr/lib/python2.7/dist-packages/django/db/backends/__init__.py", line 124, in ensure_connection
    self.connect()
  File "/usr/lib/python2.7/dist-packages/django/db/backends/__init__.py", line 112, in connect
    self.connection = self.get_new_connection(conn_params)
  File "/usr/lib/python2.7/dist-packages/django/db/backends/postgresql_psycopg2/base.py", line 116, in get_new_connection
    return Database.connect(**conn_params)
  File "/usr/lib/python2.7/dist-packages/psycopg2/__init__.py", line 179, in connect
    connection_factory=connection_factory, async=async)
django.db.utils.OperationalError: FATAL: password authentication failed for user "maas"
FATAL: password authentication failed for user "maas"