Add pkg dep for python-apt

The hacluster charm depends on python-apt but doesn't explicitly
install it. For other charms this has been working by accident as
they have had a dependancy on python-apt themselves in some way.
Fixing it in the hacluster charm is the correct approach but is
non-trivial so temporarily fix add it as a dep to this charm so it
is installed by the principle before hacluster is installed.

Related-Bug: #1606906

Change-Id: I07e575f7096aa528d85ac5f7f23318ceb44b66ac

requirements.txt

@@ -1,5 +1,4 @@
 # Requirements to build the charm
 charm-tools
-ruamel.yaml==0.10.12
 simplejson
 flake8

src/lib/charm/openstack/aodh.py

@@ -45,9 +45,11 @@ class AodhCharm(charms_openstack.charm.HAOpenStackCharm):
     release = 'mitaka'
 
     # Packages the service needs installed
+    # LY Hacluster depends on python-apt so fixing it here is a temporary
+    # tactical fix. Bug #1606906
     packages = ['aodh-api', 'aodh-evaluator',
                 'aodh-expirer', 'aodh-notifier',
-                'aodh-listener']
+                'aodh-listener', 'python-apt']
 
     # Init services the charm manages
     services = ['aodh-api', 'aodh-evaluator',